Verified Answer :

136 = 2x^2 + 8
128 = 2x^2
64 = x^2
8 = x

Zos

I would say the answer is 8:

f(x) = 2x^2 + 8
f(x) = 136
f(x) = f(x)
2x^2 + 8 = 136
Subtract both sides by 8
2x^2=128
Divide both sides by 2
x^2 = 64
Square both sides
x = 8

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