pembahasan :
x - y^2 = 1
-y^2 = -x + 1
y^2 = x - 1
x^2 + y^2 = 5
x^2 + x-1 = 5
x^2 + x-1-5 = 0
x^2 + x - 6 = 0
faktorkan:
(x+3) (x-2)
x=(-3) x=2
y^2 = x - 1
y^2 = (-3) - 1
y^2 = -4
y = V-4 ==> tidak memenuhi
y^2 = 2 - 1
y^2 = 1
y = V1
y = 1
jawaban : (x,y) = (2,1) atau = (a,b)
masukan ke soal a-3b :
a-3b =
2 -3(1) =
2 - 3 = -1