Question

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Determine the intervals where the value of f(x) is positive, when f(x)= (x + 7)(2x + 3)(x + 5). Choose all that apply
a. -∞ < x < 7
b. -7 < x < -5
c. -5 < x < -3/2
d. -3/2 < x < ∞

Answer 1

• b and d

Explanation:

Find zero's:

• x = -7
• x = -3/2
• x = -5

The intervals:

• x < -7, all negative, the result is negative
• x is between -7 and -5, two negatives, the result is positive
• x is between -5 and -3/2, one negative, the result is negative
• x is greater than -3/2, all 3 positives, the result is positive

As we see correct choices are b and d