Base and Powers

Algebra Level 1

For what value of x x does

2 2 x × 4 8 x = 8 18 ? \large2^{2x} \times 4^{8x} = 8 ^{18} ?

2 2 4 4 3 3 1 1 5 5

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5 solutions

2 2 x × 4 8 x = 2 2 x × 2 16 x = 2 18 x 2^{2x} \times 4^{8x} = 2^{2x} \times 2^{16x} =2^{18x}

8 18 = 2 3 18 = 2 54 8^{18} =2^{3*18}=2^{54}

so , 18 x = 54 18x=54 , x = 3 x=3

Munem Shahriar
Dec 24, 2018

2 2 x 4 8 x = 8 18 4 x 4 8 x = [ ( 4 1 2 ) 3 ] 18 4 9 x = 4 18 × 3 2 4 9 x = 4 27 9 x = 27 x = 3 \large \begin{aligned} 2^{2x} \cdot 4^{8x} & = 8^{18} \\ \Rightarrow 4^x \cdot 4^{8x} & = [(4^{\frac12})^3]^{18} \\ \Rightarrow 4^{9x} & = 4^{\frac{18 \times 3}2} \\ \Rightarrow 4^{9x} & = 4^{27} \\ \Rightarrow 9x & =27 \\ \implies x & = \boxed 3 \\ \end{aligned}

2 2 x × 4 8 x = 8 18 2^{2x} \times 4^{8x} = 8^{18}

2 2 x × 2 2 ( 8 x ) = 2 3 ( 18 ) 2^{2x} \times 2^{2(8x)} = 2^{3(18)}

2 x + 16 x = 3 ( 18 ) 2x + 16x = 3(18)

x = 3 \boxed{x = 3}

Chew-Seong Cheong
Dec 24, 2018

2 2 x × 4 8 x = 8 18 2 2 x × 2 2 × 8 x = 2 3 × 18 2 2 x + 16 x = 2 3 × 18 18 x = 3 × 18 x = 3 \begin{aligned} 2^{2x} \times 4^{8x} & = 8^{18} \\ 2^{2x} \times 2^{2\times 8x} & = 2^{3\times 18} \\ 2^{2x+16x} & = 2^{3\times 18} \\ \implies 18x & = 3\times 18 \\ x & = \boxed 3 \end{aligned}

Jaywon Han
Dec 28, 2018

Make all bas get 2 and make a equation with quotient 2x+16x=54 18x=54 so x=3

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