Q. The graph of f(x)=x2−2x−34 is shown. For which values of x is f(x) decreasing?
Analyze function and domain: Step 1: Analyze the function and its domain.f(x)=x2−2x−34Factorize the denominator.x2−2x−3=(x−3)(x+1)The function is undefined at x=3 and x=−1.
Determine intervals for behavior: Step 2: Determine the intervals to test for increasing or decreasing behavior. The critical points are x=3 and x=−1, splitting the real line into three intervals: (−∞,−1), (−1,3), and (3,∞).
Choose test points for derivative: Step 3: Choose test points from each interval and plug them into the derivative f′(x).f′(x)=−[(x2−2x−3)28x−8]Test points: x=−2,0, and 4.f′(−2)=−[((−2)2−2(−2)−3)28(−2)−8]=−[(4+4−3)28(−2)−8]=−[(5)28(−2)−8]=−[25(−24)]f′(0)=−[(02−2(0)−3)28(0)−8]=−[9(−8)]f′(4)=−[(42−2(4)−3)28(4)−8]=−[49(24)]
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