who is asking:student
Level of question: middle
I Was working and i ran into this problem can you help me solve it using
the substitution method?
-3x-2y=-10
x+5y=-27
and I have another question
4x=2y+23
x-6y=3
thanks
Hi,
Look at the first two equations
-3x -2y = -10
x + 5y = -27
In the second equation add -5y to each side to get
x + 5y -5y = -27 -5y
and hence
x = -27 -5y
Thus I "solved for x in terms of y", in other words I have x = (some expression involving y but no x).
Now take this expression for x and substitute it into the first equation
-3x -2y = -10, therefore
-3 ( -27 -5y) -2y = -10
Now simplify
81 + 15y - 2y = -10
81 + 13y = -10
13y = -10 -81 = -91
y = -91/13 = -7
Finally, since y = -7 you can substitute that value into x = -27 -5y to get
x = -27 -5(-7) = -27 + 35 = 8
Hence x = 8 and y = -7.
I could have started by "solving the first equation for x in terms of y" or either equation "for y in terms of x" but I made the choice I did since I could proceed without using fractions.
Now you try the second problem and write back it you have difficulty.
Penny