Your answer will turn out to be −4x^2+3x.
Simplify. Distribute -1 to all terms within the second parenthesis
-(6x² + 3x + 5) = -6x² - 3x - 5
Combine like terms
2x² - 6x² = -4x²
6x - 3x = 3x
5 - 5 = 0
-4x² + 3x is your answer
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