14
RCMultiple Choice

Trigonometric Sum Identities — Cumulative exam

Question 14 • Precalculus

What is the solution to 4x 3 – 3x 2 – 7x < 0?

Answer
A
(–ꝏ, –1) U (0, 1.75)
B
(–ꝏ, –1] U [0, 1.75]
C
(–1, 0) U (1.75, ꝏ)
D
[–1, 0] U [1.75, ꝏ)

Explanation

Factor the expression: 4x³ − 3x² − 7x = x(4x² − 3x − 7) = x(x + 1)(4x − 7). Its zeros are −1, 0, and 7/4 (or 1.75). Testing the intervals determined by these zeros shows the expression is negative on (−∞, −1) and (0, 1.75). Because the inequality is strict, the zeros are excluded, so the answer is choice A, (−∞, −1) ∪ (0, 1.75).

AI-written and checked against the verified answer.

Previous
Next