Jika g(x)=x+1 dan (f ° g)(x)=x^2+3x+1,maka f(x)=... x^2+5x+5 x^2+x-1 x^2 4x+3 x^2 6x+1 x^2+3x-1

fog(x) = x² + 3x + 1
f(x + 1) = (x + 1)² + x
f(x + 1) = (x + 1)² + (x + 1) - 1
f(x) = x² + x - 1
atau cara lain dimisalkan p = x + 1
p - 1 = x
f(p) = (p - 1)² + 3(p - 1) + 1
= p² - 2x + 1 + 3p - 3 + 1
= p² + p - 1
f(x) = x² + x - 1
sama hasilnya
B