How do you subtract #(9x ^ { 2} - 8x + 5) - ( - x ^ { 2} + 7x + 7)#?

1 Answer
anor277
Oct 15, 2016

#(9x^2-8x+5)-(-x^2+7x+7)# #=# #10x^2-15x-2#

Explanation:

#(9x^2-8x+5)-(-x^2+7x+7)#

#=# #(9x^2-8x+5)+(-1)(-x^2+7x+7)#

#=# #(9x^2-8x+5)+x^2-7x-7#

#=# #10x^2-15x-2#

Because the 2nd bracketed expression, #(-x^2+7x+7)#, was subtracted from the first expression, it was in effect mulitplied by #-1#. And thus #-1xx(-x^2+7x+7)=x^2-7x-7#.

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