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Find f'(x) for f(x) = 2x5 + 6x8. O 10x6 + 48x9 O 10x3 + 48x2 10x4 + 48x7 O 2x4 + 6x? Question 15 Find the values of x where the tangent line is horizontal for f(x) = 3x3 - 2x2 - 9. O x = 0, x = 4/9 O x = 0, x = -4/9 O x = 0, x = 2/3 O x = 0, x = -2/3 Question 16 Evaluate dy and A y for y = f(x) = x 2-7x + 5, x =7, and dx = = = 0.5. O dy = 3.75, A y = 3.5 O dy = 3.5, A y = 3.75 O dy = 3.75, A y = 3.75 O dy = 3.5, A y = 3.5