jika f(x)= ax+b, f(1)=5 q(x)=x²+1, dan (qof)(2)=50 tentukan nilai a?? tolong pakai cara

f(x) = ax + b
f(1) = a + b = 5 ...............(1)

qof(2) = q(f(2))
          = q(2a + b)
          = (2a + b)² + 1
          = 4a² + 4ab + b²  = 49 ..............(2)

dari pers. (2)
4a(a + b) + b²  = 49
4a (5) + b² = 49
20a + b² = 49
a = [49 - b²] / 20