f(x) = -3x + 7
f(x)=√(x+1)
f(x) = log x
f(x) = x^2 - 2x + 1
f(x)=(x+3)/(x-1)
f(x)=(1/2)^x
f(x) = cos x
f(x) = - x^2+3x
f(x) = sen x
