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Y=-x^2+4 => x^2 +y = 4
Y=3x-6
Subsitusi
x^2 +y = 4
x^2 + (3x-6) = 4
X^2 + 3x -6 -4 = 0
X^2 + 3x -10 =0
(X+5)(x-2)
X1= -5 dan x2=2

Y=-x^2-7x+4 => x^2+7×+y-4=0
Y=-6x-2
Subsitusi
x^2+7×+y-4=0
x^2+7×+(-6x-2)-4=0
X^2+7x-6x-2-4=0
X^2+x-6=0
(X+3)(x-2) =0
X1=-3 dan x2=2