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

1 Answer
Mar 28, 2018

Answer:

#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#