Given the function fx x2 3x Evaluate f5 Solve fx 4Solutio

Given the function f(x) = x^2 - 3x Evaluate f(5). Solve f(x) = 4

f(x) = x^2 -3x

a) f(5) ; plug x=5

f(5) = 5^2 -3*5 = 25 -15 =10

b) f(x) = 4

x^2 -3x =4 ---> x^2 -3x -4 =0

solve the quadratic by factorisation:

x^2 -4x +x -4 =0

x(x-4) +1(x-4 ) =0

(x+1)(x-4) =0

x= -1 ; x= 4