Question

Descompuneti in factori :$A)x^{2} - 4x-5 b )x^{2} -4x-21 c ) x^{2} - 6x -27 d) x^{2} +2x-3 e) x^{2} +7x-18$

Answer 1

Vom face astfel:

a)
x²+x-5x-5 ;   x(x+1)-5(x+1) <=>(x+1)(x-5)
b) x²-4x-21
x²-7x+3x-21;  x(x-7)+3(x-7) =>(x-7)(x+3)
c)
x²-6x-27
x²-9x+3x-27;  x(x-9)+3(x-9)<=>(x-9)(x+3)
d)x²+2x-3
x²+3x-x-3;  x(x+3)-(x+3) => (x+3)(x-1)
e)x²+7x-18
x²+9x-2x-18
x(x+9)-2(x+9) =(x+9)(x-2)