How do you simplify (3+ 8x ) ( 9- 8x + 7x ^ { 2} ) ?

1 Answer
Mar 28, 2018

56x^3 - 43x^2 + 48x = 27

Explanation:

Multiply everything in the second bracket by everything in the first bracket then collect like terms.
( 3 + 8x ) ( 9 - 8x + 7x^2 )
first multiply the second bracket by 3;
27 - 24x + 21x^2
now multiply the second bracket by 8x;
72x - 64x^2 + 56x^3
I would write this all on one line as I did it like so:

27 - 24x + 21x^2 + 72x - 64x^2 +56x^3

Now collect like terms so all the terms without x go together, all the terms with x, all the terms with x^2 and all the terms with x^3 etc

27 + 48x - 43x^2 + 56x^3

Then I rearranged it with the highest powers first (because I am a bit sad!)

56x^3 - 43x^2 + 48x + 27