tolong kerjain nomer 7 dan 9 buat ulangan besok

7. f(4) = 4a+b=5
    f(-2) = -2a+b = -7 terus dikurangin hasilnya 6a = 12 jadi a = 2
    jadi bnya = -3
a. nilai a = 2
    niali b = -3
b. f(x) = 2x-3

9. f(2) = 2a+b = -2
    f(3) = 3a + b=13 terus f(3) dikurang f(2) = a= 15
    b = -32
f(4) = 15(4) -32
      = 28