Q. f(x)=(5x+3)(x−2)(3x+7)(x+5) has zeros at x=−5,x=−37,x=−53, and x=2.What is the sign of f on the interval −37<x<−53 ?Choose 1 answer:(A) f is always positive on the interval.(B) f is always negative on the interval.(C) f is sometimes positive and sometimes negative on the interval.
Identify Zeros:f(x) has zeros at x=−5, x=3−7, x=5−3, and x=2. To determine the sign of f(x) on the interval \frac{-7}{3} < x < \frac{-3}{5}, we need to test a value within this interval.
Choose Test Value: Choose a test value between −37 and −53, let's pick x=−1. Substitute x=−1 into f(x) to determine the sign.
Substitute and Determine Sign:f(−1)=(5(−1)+3)((−1)−2)(3(−1)+7)((−1)+5)=(−2)(−3)(4)(4)=96. Since 96 is positive, f(x) is positive for our test value.
Continuity and Sign: Since f(x) is a polynomial function, it is continuous and will not change sign between zeros unless it crosses a zero. There are no zeros of f(x) between −37 and −53, so f(x) must be positive throughout this interval.
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