Question

If 2^(x+3) - 2x = k(2^x) what is the value of k

Answer 1

Answer:

$\large\boxed{C)\ 7}$

Step-by-step explanation:

Use:

$a^n\cdot a^m=a^{n+m}$

$2^{x+3}-2^x=2^x\cdot2^3-2^x=8\cdot2^x-2^x=(8-1)\cdot2^x=7\cdot2^x\\\\2^{x+3}-2^x=k(2^x)\\\\7\cdot2^x=k(2^x)\Rightarrow k=7$

$8\cdot2^x-2^x=8\cdot2^x-1\cdot2^x=(8-1)(2^x)=7\cdot2^x\\\\\text{distributive property:}\ a(b-c)=ab-ac$