Đáp án:
Giải thích các bước giải:
a) x^2 - 5x + 6
= x^2 - 2x - 3x + 6
= (x^2 - 2x) - (3x - 6)
= x(x - 2) - 3(x - 2)
= (x-2)(x-3)
b) 3x^2 + 9x - 30
= 3( x^2 + 3x - 10 )
= 3( x^2 -2x + 5x - 10)
= 3 [ ( x^2 - 2x ) + ( 5x - 10) ]
= 3 [ x ( x - 2 ) + 5( x - 2 ) ]
= 3(x-2)(x+5)
c) x^2 - 3x + 2
= x^2 - x - 2x + 2
= (x^2 - x) - (2x - 2)
= x(x-1) - 2(x-1)
= (x-1)(x-2)
d) x^2 - 9x + 18
= x^2 - 3x - 6x + 18
= ( x^2-3x) - (6x-18)
= x(x-3) - 6(x-3)
= (x-3)(x-6)
e) x^2 - 6x + 8
= x^2 - 2x - 4x + 8
= ( x^2-2x ) - ( 4x-8)
= x(x-2) - 4(x-2)
= (x-2)(x-4)
f) x^2 - 5x -14
= x^2 + 2x - 7x - 14
= (x^2 + 2x) - (7x + 14)
= x(x+2) - 7(x+2)
= (x+2)(x-7)
g) x^2 + 6x + 5
= x^2 + x + 5x + 5
= (x^2 + x) + (5x + 5)
= x(x+1) + 5(x+1)
= (x+1)(x+5)
h) x^2 - 7x + 12
= x^2 - 4x - 3x + 12
= ( x^2 - 4x) - (3x-12)
= x(x-4) - 3(x-4)
= (x-4)(x-3)
i) x^2 - 7x + 10
= x^2 - 5x - 2x + 10
= ( x^2-5x) - (2x-10)
= x(x-5) - 2(x-5)
= (x-5)(x-2)
