Respuesta :

x^2-3x = x(x-3)
x^2-9 = x^2 - 3^2 = (x-3)(x+3)
HCF = x-3
x²-3x=x(x-3)
x²-9=x²-3²=(x-3)(x+3)
∴the highest common factor of x²-3x and x²-9 is x-3

Hope my answer helped u :)