Question 290744

(-8x7 + 5x9 - 1 + 3x8) - (7 + 7x8 + 7x9 + 2x7) 

= {{{(-8x^7+5x^9-1+3x^8)-(7+7x^8+7x^9+2x^7)}}}..Let us now remove the curved brackets.  Keep one thing in your mind : if negative sign is found immediately before the bracket, then change all the signs inside the bracket.  In the second bracket, we find -ve sign before the bracket starts. so we will change all the signs inside the bracket.
= {{{-8x^7+5x^9-1+3x^8-7-7x^8-7x^9-2x^7}}}  Now arrange the terms degree-wise   and simplify.
= {{{5x^9-7x^9+3x^8-7x^8-8x^7-2x^7-1-7}}}
= {{{-2x^9-4x^8-10x^7-8}}}  Answer.  

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