The Power of Absolute - 2

Algebra Level 4

25 + 3 ( 15 ) x = 5 x + 25 ( 3 x + 1 ) \large25+3(15)^{|x|}=5^{|x|}+25\left(3^{|x|+1}\right)

Find the product of all values of x x satisfying the above equation.


The answer is -4.

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1 solution

Sahil Bansal
Mar 26, 2016

The above equation can be written as: 25 + 3 ( 5 3 ) x = 5 x + 25 ( 3 x + 1 ) 25+3(5*3)^{\left | x \right |}=5^{\left | x \right |}+25(3^{\left | x \right |+1})

25 + 5 x ( 3 x + 1 ) = 5 x + 25 ( 3 x + 1 ) \Rightarrow 25+5^{\left | x \right |}(3^{\left | x \right |+1})=5^{\left | x \right |}+25(3^{\left | x \right |+1})

5 x ( 3 x + 1 1 ) = 25 ( 3 x + 1 1 ) \Rightarrow 5^{\left | x \right |}(3^{\left | x \right |+1}-1)=25(3^{\left | x \right |+1}-1)

( 3 x + 1 1 ) ( 5 x 25 ) = 0 \Rightarrow (3^{\left | x \right |+1}-1)(5^{\left | x \right |}-25)=0

Hence, either 3 x + 1 1 = 0 3^{\left | x \right |+1}-1=0 or 5 x 25 = 0 5^{\left | x \right |}-25=0

3 x + 1 = 1 \Rightarrow 3^{\left | x \right |+1}=1 or 5 x = 25 5^{\left | x \right |}=25

x + 1 = 0 \Rightarrow \left | x \right |+1=0 or x = 2 \left | x \right |=2

x = 1 \Rightarrow \left | x \right |=-1 (This is not possible) or x = ± 2 x=\pm 2

Hence, x = ± 2 x=\pm 2 are the only possible values that x can take.

Therefore, product of all values of x satisfying the given equation is: 2 ( 2 ) = 4 2*(-2)=\boxed{-4}

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