







Integration of dx/(x^2+1)^3 
20160107 

From Ishank: Integration of dx/(x^2+1)^3 Answered by Penny Nom. 





A linear system 
20141014 

From pheter: 4/x  1/y = 3 .... equation (1)
6/x  2/y = 5 .... equation (2) Answered by Penny Nom. 





Evaluate x(3x+5) if x=2 
20140403 

From Destiny: I wanted to know the value of x(3x+5) if x=2 Answered by Penny Nom. 





f(x)= a+b*lnx 
20131204 

From Kevin: How do I find the curve, algebraically on paper, for f(x)= a+b*lnx with data points
(6,1303) (9,1639). I can do it with LnReg on a calculator but I want to know how
to get the same results or close to the same results by working it out on paper.
When I run it through the LnReg on the calculator I get, f(x)=181.792+828.678 Ln x.
How did it achieve this solution? Answered by Penny Nom. 





Substitution type simultaneous equations 
20131103 

From Kayla: I am having problems with substitution type simultaneous equations, when the variable you are substituting is a algebraic one:
y=x^23x+4 and 3x2y=1
I have rearranged 3x2y=1 to get x=(1+2y)/3 but when I substitute this x value into the other equation, I get the wrong answers!
Would appreciate any help! Thank you. Answered by Penny Nom. 





Integral 1/(25x^2)^3/2 
20120222 

From John: Integral 1/(25x^2)^3/2 Answered by Harley Weston. 





Elimination and substitution 
20100918 

From Lauren: Solve one using the method of substitution and the other with the method of elimination.
v
a. y=5x+4
x=2y+1
b. 4x+3y=7
6x3y=13 Answered by Penny Nom. 





y = kx 
20100326 

From harold: if y =kx and y =4/15 and x=2/3, what is value of k Answered by Penny Nom. 





The integral of X^3/the square root of 1x^2 dx 
20100307 

From William: The integral of X^3/the square root of 1x^2 dx. Answered by Harley Weston. 





Substitution method 
20100217 

From Melodie: 7x  4y = 10
4y= x2 Answered by Tyler Wood. 





Substitution 
20100214 

From Izayah: what is 3 ways to find the meeting point of y=2x+4 and 3x+y=7
by making 2 table and using a graph Answered by Stephen La Rocque. 





An integral 
20100129 

From amr: find the value of the following integral:
(1+x)power (1/2) dx Answered by Robert Dawson. 





The method of substitution 
20090917 

From laura: ok! i really need help with this question plz help!!
x=  4y +5
x+2y = 7 Answered by Penny Nom. 





Substitution in a quadratic 
20090309 

From Kieran: How could I work this out please
f(x)= 3xsquared  4x + 2
if f(2x) Answered by Penny Nom. 





Linear systems 
20090220 

From Rose: I have been having trouble trying to figure out these three math problems , I need help breaking them down so I could understand them better please help.
1. x = 7  x
2 x  y + 8
2. 8 x + 5 y = 1 8 4
x  y = 3
3. y + 2 x = 3
y + 2 x = 4
I can't figure out how to break them down in the right order. Answered by Penny Nom. 





The substitution method 
20090218 

From Nicolette: I am working on linear programming problems that I need to solve pairs of linear equations for. I am confused and am not sure how to solve these problems!
5x+3y=7 y=x3 How can i solve this using the substitution method? Answered by Penny Nom. 





A definite integral 
20090209 

From Mathata: Evaluate: integral from 0 to 1, x^2 e^x^3dx Answered by Harley Weston. 





The substitution method 
20090206 

From amber: Pleasse help me with this problem
x+y=2
y2x=1 Answered by Penny Nom. 





The integral of f(x)dx and the integral of f(x4)dx 
20090102 

From Katie: Calculus:
If the definite integral from 2 to 6 of f(x)dx=10 and the definite integral from 2 to 6 of f(x)dx=3, then the definite integral from 2 to 6 of f(x4)dx= ?
I don't understand how to solve definite integrals when the function has something more than just x inside the parenthesis such as f(4x). Answered by Robert Dawson. 





The substitution method 
20080726 

From Enid: Solve by substitution method
3x + 7y = 25
7x + y = 63 Answered by Penny Nom. 





A rectangular room 
20080630 

From Peter: A rectangular room has a perimeter of 42 feet and an area of 108 square feet. What is the length, in feet, of the shorter side? Answered by Penny Nom. 





Substitution into a formula 
20080602 

From beth: Given q(x) = 7xsquared + 9, find q(7)
These were the choices I had for the answers to this problem
1.) 343
2.) 40
3.) 334
4.) 89
5.) 352 Answered by Penny Nom. 





Substitution method 
20080530 

From taquicia: 2yx=3
x=5+y Answered by Janice Cotcher. 





Integrate 2x(x^21)^5 dx 
20080417 

From joey: pls help me to integrate
2x(x^21)^5 dx using the substitution u=x^21 Answered by Harley Weston. 





The integral of dx / (4x^2  25)^3/2 
20080401 

From Meghan: I have a question from the trigonometric substitution of my calculus course.
integral of dx / (4x^2  25)^3/2 Answered by Harley Weston. 





An integral 
20080124 

From Meghan: Evaluate the indefinite integral of (x^3 +1)^(1/3) * x^5 * dx. Answered by Brennan Yaremko. 





Substitution method 
20071011 

From Kevin: 3xx+2y=36y=11 Answered by Stephen La Rocque. 





Two equations in two unknowns 
20070922 

From Mary: Having problems doing this problem, looking for a solution with the work. I would like to see how you got your answer, to see what I was doing wrong.
solve using the substitution method, is there "no solution" or "infinitely many solutions"
4x+y=4
2x+8y=0 Answered by Stephen La Rocque and Leeanne Boehm. 





Solve by substitution 
20070728 

From Marina: I am stuck with this substition please help.
3x+y=1
5x+2y=4 Answered by Penny Nom. 





The substitution method 
20070623 

From mary: solve the system by the method of substitution:
5x+2y=15
4xy=9 Answered by Stephen La Rocque. 





The substitution method 
20070508 

From A student: I need help on these two problems( substitution method)
2x+7y=10
x3y= 3
and
6x8y= 12 3x+4y=9 Answered by Penny Nom. 





Solve for x and y 
20070327 

From anthony: solve y=4x and x+y=5 Answered by Sara Ulmer. 





Simultaneous equations with fractions 
20070228 

From Alyca: Hello Math Central, I am a grade 10 student taking Academic math. Our unit right now is method of substitution and elimination. I'm stuck on this one question that I've been doing forever. Please help =)
*For this equation I have to do method of elimination, but it's so much harder with fractions...could some one please explain to me how to do it step by step?* x y 2    =   3 6 3 x y 1    = 1 12 4 2
Answered by Steve La Rocque and Ashley Mang. 





The substitution method 
20070131 

From Victoria: how do i solve this problem using the substitution method? 2x5= 14 7x+14y= 5 Answered by Stephen La Rocque. 





The substitution method 
20050628 

From Addie: how do i know where to began the substitution method? how do i solve
y = x + 1
2x  y = 1 Answered by Penny Nom. 





The substitution method 
20041128 

From A student: I Was working and i ran into this problem can you help me solve it using the substitution method?
3x2y=10
x+5y=27 Answered by Penny Nom. 





The method of substitution 
20040920 

From Kayla: y=x1
y=2x3 Answered by Harley Weston. 





x^2/3  7 x^1/3 + 12 = 0 
20040405 

From Jackie: I am having trouble solving this question for x:
1.) x^2/3  7 x^1/3 + 12 = 0 Answered by Penny Nom. 





The substitution method 
20040214 

From Keisha: I need to solve this problem by using the substitution method.
3x+y=1
x=2y+5
Please help me understand the method to solve. Answered by Penny Nom. 





Systems of equations 
20031119 

From Scott: I hope that u can help me....I
am a college student taking a class in Pre Calculus.....I have homework
due this Friday and it counts a BIG Percentage on my FINAL grade.....I
am getting mixed up and can not figure out a few problems.....Please help
me.....
Method Of Subsitution
Problem 1. y 8x = 5
x(squared) + y(squared) = 25
Problem 2. y = x(squared)  2x  6
Y = x(squared)  4
Answered by Penny Nom. 





5x  y 
20031011 

From Candace: math problem 5xy for x=12 and y=14 do you mulitilpy 5x12 and than the answer from 14 which gives you 46? is this right Answered by Penny Nom. 





Substitution method 
20030914 

From John:
Hello, my name is john and while I was finishing up my work I stumbled into these problems. a/4b=1 a+b=11 and 6ab=5 4a3b=8 Thanks a lot. I really need some help :) John Answered by Penny Nom. 





Two equations 
20030821 

From Jennifer:
The following problems have me stuck and any help would be greatly appreciated seeing my text book is doing me no favours:
3^{2a+1}  283^{a} + 9=0 and 5^{2m}  5^{m}=20 Answered by Penny Nom. 





The substitution method 
20030414 

From Patty:
I need help with the following: 5x  4y = 13 2y + 3x = 1 Answered by Penny Nom. 





The substitution method 
20021115 

From A student: Solve by using the substitution method. x = 3y  1 x + 2y = 9 Answered by Penny Nom. 





Substitution 
20021106 

From John Paul: I took a math test last week, and there was a problem which the teacher checked as incorrect. It was:
Solve: (a)RcTc=360;(b)RmTm=480;(c)Rm=2Rc; (d)Tm+Tc=15 I solved the problem and I got the following values for each variable.
For Rc=40 For Tc=9 For Rm=96 For Tm=5 I don't see nothing wrong, but the teacher checked it as wrong. Could it be a checking mistake? Answered by Claude Tardif. 





18m11+ 7 
20021106 

From Sophia: what is 18m11+ 7 (m = to 12)? Answered by Penny Nom. 





Algebra 
20020908 

From Heather: This question is from an 8th grade Algebra classs. I am a parent asking for help to explain to my child. Q: d=25t^{2}. Answered by Leeanne Boehm. 





x + 5 + x, if x = 4 
20020723 

From Elisa: x + 5 + x, if x = 4 Answered by Leeanne Boehm. 





The substitution method 
20020224 

From Joe: whats the answer to this question? 3x+y=11 x+2y=3 its substitution method i am having alot of trouble figuring it out. send the answer as soon as possible. thank you Answered by Penny Nom. 





The substitution method 
20010305 

From A student: Solve each system of equations by the substitution method. Show your work.  y = 8
7x = 1  y
 y = x  1
4x  y = 19 Answered by Penny Nom. 





Some integration problems 
20000223 

From Tim Valentine: I am having a great deal of difficulty with the following integrals, can you help? I think they need the use of trig substitution or integration by parts but I cannot figure out how to begin. Thanks! The integral of 1/(2+3x^{2}) dx. and The integral of x * square root of (4x+5) dx. Answered by Harley Weston. 





Algebre 
20090304 

From Jonnathan: Pour entrer sur le site d'une exposition, il en coute 41$ pour 2 enfants et 2 adultes mais 37.50$ pour 3 enfants et un adulte. Quel est le prix de la rentree pour l'enfant et quel est le prix de la rentree pour l'adulte? il faut utiliser la methode de comparaison ou de substitution Answered by Claude Tardif. 

