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Dacă x^2 - 5x + 6 = (x + a) (x + b) , a x b = ?

Răspuns :

x²-5x+6=x²-2x-3x+6=x(x-3)-2(x-3)=(x-3)(x-2)
a=-3, b=-2
a*b=-3*(-2)=6.
x^2-3x-2x+6=x^2+bx+ax+ab
(x-3)(x-2)=x(x+b)+a(x+b)
(x-3)(x-2)= (x+a)(x+b) => a=-3 ; b=-2 => a×b=6