9514 1404 393
Answer:
(b) -3
Step-by-step explanation:
It can work well to rewrite the equation as powers of 2.
[tex]4^x=\left(\dfrac{1}{8}\right)^{x+5}\\\\(2^2)^x=(2^{-3})^{x+5}\qquad\text{as powers of 2}\\\\2x=-3(x+5)\qquad\text{equate exponents}\\\\5x=-15\qquad\text{add $3x$}\\\\\boxed{x=-3}\qquad\text{divide by 5}[/tex]
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Check
4^-3 = (1/8)^(-3+5) ⇒ 1/64 = (1/8)^2 . . . . true
