SEARCH HOME
Math CentralQuandaries & Queries

search

Question from gagan, a student:

find all the roots of z^5-3z^4+2z^3+z^2-3z+2

Hi,

Many times the key to solving an algebra problem is recognizing a pattern. It's like hearing the first few bars of a song for the first time and knowing immediately the group that is performing it. That skill you get from hearing the group so many time s that you easily recognize its sound. The same is true of algebra. If you have worked with algebraic expressions often enough you see patterns.

What I see in The expression z5 - 3z4 + 2z3 + z2 - 3z + 2 is

(z5 - 3z4 + 2z3) + (z2 - 3z + 2).

I have grouped the terms in this way because the coefficients match, 2, -3 and 2. Hence I can write the expression

z3 (z2 - 3z + 2) + (z2 - 3z + 2)

and see (z2 - 3z + 2) as a common factor so that the expression becomes

(z3 + 1)(z2 - 3z + 2)

Can you complete the problem from here?

Write back if you need more assistance,
Penny

 

Hi Gagan. Look for factoring opportunities first.

See the coefficients: 1, -3, 2, 1, -3, 2. There's a repeated group, so
we can factor:

(z2 - 3z + 2) (z3 + 1)

Now can you finish factoring and solve the problem?

Write back if you need more help.
Stephen La Rocque

About Math Central
 

 


Math Central is supported by the University of Regina and The Pacific Institute for the Mathematical Sciences.
Quandaries & Queries page Home page University of Regina PIMS