Question

Solve part 3rd and it's answer is -2x^3 - x^2 + 3x - 12 but when I m solving it my answer is coming 5x^3 + 7x - 12. Please solve it and tell me what mistake I am doing.
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. please don't spam coz today is my test.​

Answer 1

Step-by-step explanation:

x^3+3x-9 to get 3x^3+x^2+3

=(x^3+3x-9) - (3x^3+x^2+3)

=x^3+3x-9-3x^3 -x^2 -3

=x^3-3x^3 -x^2 +3x-9-3

= - 2x^3 - x^2 +3x -12