Question 384057
{{{(-4 - 2x^5 + 9x^7 - 8x^6) - (x^6 + 4x^5 + 4 + 3x^7)}}}
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STEP 1
remove the parenthesis
{{{(-4 - 2x^5 + 9x^7 - 8x^6 - x^6 - 4x^5 - 4 - 3x^7)}}}
(Note that when you remove the parenthesis the terms are written as opposites since there is a negative sign before the parenthsis). 
STEP 2
(group the similar terms with their signs starting from highest index to constant)
{{{(9x^7-3x^7-8x^6-x^6-2x^5-4x^5-4-4)}}}
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STEP 3
Add the like terms 
{{{(6x^7-9x^6-6x^5-8)}}}
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{{{(highlight(6x^7-9x^6-6x^5-8))}}}
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