If 2^{x+1} + 2^{x-1} = 320, what is the value of x? — State PSC Exam

If $2^{x+1} + 2^{x-1} = 320$ , what is the value of $x$ ?

Answer: 7

The value of

x

is 7.

Factoring out

2^{x-1}

from the expression gives

2^{x-1}(2^2 + 1) = 320

, which simplifies to

5 \cdot 2^{x-1} = 320

. Dividing by 5 yields

2^{x-1} = 64 = 2^6

. Equating exponents gives

x - 1 = 6

, so

x = 7

Rewrite terms using exponent rules to factor out the common power

2^{x-1}

2^{x-1}(2^2 + 1) = 320

Using the product rule

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

, we have

2^{x+1} = 2^{x-1} \cdot 2^2

Simplify the numerical factor inside the parentheses

5 \cdot 2^{x-1} = 320

2^2 + 1 = 4 + 1 = 5

Isolate the exponential term by dividing by 5

2^{x-1} = 64

Dividing

320

5

gives

64

Write 64 as a power of 2 and solve for

x

2^{x-1} = 2^6 \implies x - 1 = 6 \implies x = 7

Equating exponents when bases are equal.

Solving Exponential Equations by Factoring Common Powers

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