Test to see whether the following functions are increasing, decreasing, or stationary at x = 3. (a)

Test to see whether the following functions are increasing, decreasing, or stationary at x = 3.

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(a) y = 5x212x+8 y' = 10x12 y' (3) 10(3) 12 = 18 > 0 (b) y=x-4x - 9x+19 = - y' = 3x - 8x-9 y' (3)=3(3) 8(3) - 9 = 6 < 0 - function is increasing function is decreasing (c) y=x4-9x + 22.5x-92 y' = 4x-27x2 +45x y' (3)=4(3) 27(3) + 45(3) = 0 function is stationary