G(x)=2x+1 dan (f o g)=4x^2+4x+5 f(x)?

Fog(x)= 4x^2 + 4x + 5 , g(x)= 2x + 1
F(g(x))= 4x^2 + 4x + 5
F(2x + 1)= 4x^2 + 4x + 5
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Misal,
2x + 1 = y
X = (y - 1)/2 [ jadi, x-nya diganti sama (y - 1)/2 ]
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F(x)= 4((y - 1)/2)^2 + 4((y - 1)/2) + 5
F(x)= 4((y^2 - 2y + 1)/4) + (2y - 2) + 5
F(x)= (y^2 - 2y + 1) + (2y - 2) + 5
F(x)= y^2 + 4
F(x)= x^2 + 4