Question 601713
Question:  Multiply
x – 2
by
-5x2 – 3x – 4 

Answer:  
(x – 2)(-5x^2 – 3x – 4 )
= 5x^3 - 3x^2 - 4x + 10x^2 + 6x + 8
= 5x^3 - 3x^2 + 10x^2 - 4x + 6x + 8
= 5x^3 + 8x^2 + 2x + 8
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It's -5x^3, and
 -3x^3+10x^3 = 7x^2
= -5x^3 + 7x^2 + 2x + 8
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Question:  Subtract.
(4n6 – 7n5 + 5) – (9n6 – n5 + 8) 

Answer: 
4n^6 - 7n^5 + 5 - 9n^6 + n^5 - 8
= (4 -9)n^6 + (7 - 1)n^5 - 3
=(-5) n^6 + (-6)n^5 - 3
= -5n^6 - 6n^5 -3
Looks good.