Algebra: Solve and explain please....?

Question

(-8x^3-8x^2+5)(2x^2-x)

I get to the last line and then have trouble combining terms.

Answer 1

I do the box method for these to keep from getting confused. Draw a 3x2 box, then put each term of the trinomial on top of the 3 columns and each term of the binomial beside each row. Then multiply rows by columns and put the answer in the box. Then just combine everything.

............-8x^3..| -8x^2...| +5...
2x^2 | -16x^5 | -16x^4 | 10x^2
-x......| 8x^4....| 8x^3.....| -5x

-16x^5 - 16x^4 + 8x^4 + 8x^3 + 10x^2 - 5x
-16x^5 - 8x^4 + 8x^3 + 10x^2 - 5x

Answer 2

You "solve" only if there is an equation ie an = sign required.
We will multiply out the brackets:-
- 16 x^5 + 8x^4 - 16x^4 + 8x³ + 10x² - 5x
- 16 x^5 - 8 x^4 + 8x³ + 10x² - 5x

Answer 3

(-8x^3 - 8x^2 + 5)(2x^2 - x)
= -16x^5 - 16x^4 + 10x^2 + 8x^4 + 8x^3 -5x
= -16x^5 - 8x^4 + 8x^3 + 10x^2 - 5x
Can't combine much.

Answer 4

(-8x^3-8x^2+5)(2x^2-x)
2x^2 [-8x^3-8x^2+5] - x [-8x^3-8x^2+5]
[-16x^5 - 16x^4 + 10x^2] - [-8x^4-8x^3+5x]
-16x^5 + [- 16x^4 + 8x^4] + 8x^3 + 10x^2 - 5x
-16x^5 - 8x^4 + 8x^3 + 10x^2 - 5x