Question

Demonstrati identitatea
a) a²+3a+2=(a+1)(a+2)
b)x²-x-6=(x-3)(x+2)

Answer 1

a)a²+3a+2=(a+1)(a+2)
a²+a+2a+2=(a+1)(a+2)
a(a+1)+2(a+1)=(a+1)(a+2)
(a+2)(a+1)=(a+1)(a+2) (adevarat)

b)x²-x-6=(x-3)(x+2)
x²-3x+2x-6x=(x-3)(x+2)
x(x-3)+2(x-3)=(x-3)(x+2)
(x+2)(x-3)=(x-3)(x+2) (adevarat)

Am folosit artificiu de calcul.