Răspuns:
Explicație pas cu pas:
a) 2x²-x-1=x²+x²-x-1=(x²-1)+(x²-x)=(x+1)(x-1)+x(x-1)=(x-1)(x+1+x)=(x-1)(2x+1)
b) 12x²-4x-1=4x²+8x²-4x-1=(4x²-1)+(8x²-4x)=(2x-1)(2x+1)+4x(2x-1)=
(2x-1)(2x+1+4x)=(2x-1)(6x+1)
c) 20x²+x-1=16x²+4x²+x-1=(16x²-1)+(4x²+x)=(4x+1)(4x-1)+x(4x+1)=(4x+1)(4x-1+x) =(4x+1)(5x-1)
d) 4x²+9x+5=4x²+4x+5x+5=4x(x+1)+(5(x+1)=(x+1)(4x+5)
e) 2x²-5x+3=2x²-2x-3x+3=2x(x-1)-3(x-1)=(x-1)(2x-3)
f) 3x²-7x+4=3x²-3x-4x+4=3x(x-1)-4(x-1)=(x-1)(3x-4)
A fost folosita formula de calcul prescurtat a²-b²=(a+b)(a-b)
