5^x+2 + 5^x=26

`5^(x + 2) + 5^x = 26`

`=> 5^x . 5^2 + 5^x = 26`

`=> 5^x (5^2 + 1) = 26`

`=> 5^x . 26 = 26`

`=> 5^x = 26 : 26`

`=> 5^x = 1`

`=> 5^x = 5^0`

`=> x=  0`

Vậy `x=  0`

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