21. \(6x^2-7x-3=\left(2x-3\right)\left(3x+1\right)\)
22.\(-12x^2+11x-2=\left(3x-2\right)\left(-4x+1\right)\)
23.\(-x^2+2x+3=\left(x+1\right)\left(-x+3\right)\)
24.\(2x^2+5x-3=\left(2x-1\right)\left(x+3\right)\)
Lời giải:
21.
$6x^2-7x-3=(6x^2+2x)-(9x+3)=2x(3x+1)-3(3x+1)=(2x-3)(3x+1)$
22.
$-12x^2+11x-2=(-12x^2+3x)+(8x-2)$
$=-3x(4x-1)+2(4x-1)=(4x-1)(-3x+2)$
23.
$-x^2+2x+3=(-x^2-x)+(3x+3)=-x(x+1)+3(x+1)=(-x+3)(x+1)$
24.
$2x^2+5x-3=(2x^2-x)+(6x-3)=x(2x-1)+3(2x-1)=(x+3)(2x-1)$
21) 6x² - 7x - 3
= 6x² + 2x - 9x - 3
= (6x² + 2x) - (9x + 3)
= 2x(3x + 1) - 3(3x + 1)
= (3x + 1)(2x - 3)
22) -12x² + 11x - 2
= -12x² + 8x + 3x - 2
= (-12x² + 8x) + (3x - 2)
= -4x(3x - 2) + (3x - 2)
= (3x - 2)(1 - 4x)
23) -x² + 2x + 3
= -x² - x + 3x + 3
= (-x² - x) + (3x + 3)
= -x(x + 1) + 3(x + 1)
= (x + 1)(3 - x)
24) 2x² + 5x - 3
= 2x² + 6x - x - 3
= (2x² + 6x) - (x + 3)
= 2x(x + 3) - (x + 3)
= (x + 3)(2x - 1)
