<h3>
Answer: 4x^3 + 2x^2 + 2x</h3>
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Work Shown:
f(x) - g(x) = [ f(x) ] - [ g(x) ]
f(x) - g(x) = [9x^3+2x^2-5x+4] - [5x^3-7x+4]
f(x) - g(x) = 9x^3+2x^2-5x+4-5x^3+7x-4 .... see note below
f(x) - g(x) = (9x^3-5x^3) + 2x^2 + (-5x+7x) + (4-4)
f(x) - g(x) = 4x^3 + 2x^2 + 2x + 0
f(x) - g(x) = 4x^3 + 2x^2 + 2x
note: distribute the negative to EVERY term inside the second set of brackets. So that is how 5x^3-7x+4 turns into -5x^3+7x-4. Basically every sign flips from positive to negative, or vice versa.