SOLUTION: I have this equation and i have tried many a times and continue to get it wrong. It is multiplying polynomials. This is the original equation (2x^2-5x-1)(x^2+x-3) and thi

Algebra ->  Polynomials-and-rational-expressions -> SOLUTION: I have this equation and i have tried many a times and continue to get it wrong. It is multiplying polynomials. This is the original equation (2x^2-5x-1)(x^2+x-3) and thi      Log On


   



Question 281508: I have this equation and i have tried many
a times and continue to get it wrong.
It is multiplying polynomials.
This is the original equation
(2x^2-5x-1)(x^2+x-3)
and this is what ive tried.
2x^2(x^2)3x^4
2x^2(x)3x^3
2x^2(-3)-6x^2
-5x(x^2)-5x^3
-5x(x)-5x^2
-5x(-3)15x
-1(x^2)-1x^2
-1(x)-1x
-1(-3)3

And this is my answer.
3x^4+3x^3-12x^2+14x-5x^3+3

Found 2 solutions by Mathematicians, JBarnum:
Answer by Mathematicians(84) About Me  (Show Source):
You can put this solution on YOUR website!
I see a couple errors when doing this:
%282x%5E2-5x-1%29%28x%5E2%2Bx-3%29
You have the right general method in mind, but the multiplication is coming out differently. For example:
2x%5E2+%2A+x%5E2+=+2x%5E4
You multiply the numbers in front, so 1+%2A+2+=+2 and it looks like you have variables down but x%5E2+%2A+x%5E2+=+x%5E4 when you put them together, you get 2x%5E4
Going through the rest of the problem:

Which is equal to:
2x%5E4+%2B+2x%5E3+-+6x%5E2+-5x%5E3+-+5x%5E2+%2B+15x+-+x%5E2+-+x+%2B+3
Combining like terms:
2x%5E4+-3x%5E3+-12x%5E2+%2B+14x+%2B+3
That should be your final answer! ^_^

Answer by JBarnum(2146) About Me  (Show Source):
You can put this solution on YOUR website!
(2x^2-5x-1)(x^2+x-3)
its easier if u seperate it into 3 multiplication and then add them together
#1) 2x%5E2%28x%5E2%2Bx-3%29
2x%5E4%2B2x%5E3-6x%5E2
#2) -5x%28x%5E2%2Bx-3%29
-5x%5E3-5x%5E2%2B15x
#3) -1%28x%5E2%2Bx-3%29
-x%5E2-x%2B3
now add the results together by adding like terms
%282x%5E4%2B2x%5E3-6x%5E2%29%2B%28-5x%5E3-5x%5E2%2B15x%29%2B%28-x%5E2-x%2B3%29
2x%5E4%2B2x%5E3-5x%5E3-6x%5E2-5x%5E2-x%5E2%2B15x-x%2B3i organize them to make it easier to see what to add
highlight%282x%5E4-3x%5E3-12x%5E2%2B14x%2B3%29