Đáp án:
a) A= x² - 8x + 7
C1: A= x² - 8x + 7
= x² - 7x - x + 7
= x( x - 7 ) - ( x - 7 )
= ( x - 1 ) ( x - 7 )
C2: A= x² - 8x + 7
= x² - x - 7x + 7
= x ( x - 1 ) - 7 ( x - 1 )
= ( x - 7 ) ( x - 1 )
b) B= x² - 7x + 10
C1: B= x² - 7x + 10
= x² - 2x - 5x + 10
= x ( x - 2 ) - 5 ( x - 2 )
= ( x - 5 ) ( x - 2 )
C2: B= x² - 7x + 10
= x² - 5x - 2x + 10
= x ( x - 5 ) - 2 ( x - 5 )
= ( x - 2 ) ( x - 5 )
c) C= 3x² - 10x + 3
C1: C= 3x² - 10x + 3
= 3x² - 9x - x + 3
= 3x ( x - 3 ) - ( x - 3 )
= ( 3x - 1 ) ( x - 3 )
C2: C= 3x² - 10x + 3
= 3x² - x -9x + 3
= x ( 3x - 1 ) - 3 ( 3x - 1 )
= ( x - 3 ) ( 3x - 1 )
d) D= 5x² + 26x + 5
C1: D= 5x² + 26x + 5
= 5x² + 25x + x + 5
= 5x ( x + 5 ) + ( x + 5 )
= ( 5x + 1 ) ( x + 5 )
C2:D= 5x² + 26x + 5
= 5x²+ x + 25x + 5
= x ( 5x + 1 ) + 5 ( 5x + 1)
= ( x + 5 ) ( 5x + 1)
e) E = 3x² - 13x + 14
C1: E = 3x² - 13x + 14
= 3x² - 7x - 6x + 14
= x ( 3x - 7 ) - 2 ( 3x - 7 )
= ( x - 2 ) ( 3x - 7 )
C2:E = 3x² - 13x + 14
= 3x² - 6x - 7x + 14
= 3x ( x - 2 ) - 7 ( x - 2 )
= ( 3x - 7 ) ( x - 2 )
f) F= 5x² - 17x + 6
C1: F= 5x² - 17x + 6
= 5x² - 15x - 2x + 6
= 5x ( x - 3 ) - 2 ( x - 3 )
= ( 5x - 2 ) ( x - 3 )
C2: F= 5x² - 17x + 6
= 5x² - 2x - 15x + 6
= x ( 5x - 2 ) - 3 ( 5x - 2 )
Câu này mình nghĩ bạn ghi sai đề + 6 chứ không phải - 6
Nên mình làm theo đề là 5x² - 17x + 6 nha
g) G = 6x² - 13x + 6
C1:G = 6x² - 13x + 6
= 6x²- 4x- 9x+ 6
= 2x ( x - 2 ) - 3x
= (2x- 3)(3x- 2)
C2:G = 6x² - 13x + 6
= 6x² - 9x - 4x + 6
= 3x ( 2x - 3 ) - 2 ( 2x - 3 )
= ( 3x - 2 ) ( 2x - 3 )
h) H= 8x² - 23x + 5
Câu này mình k phân tích được :<< Sorry
i) I = 6x² - 11x + 3
C1: I = 6x² - 11x + 3
= 6x² - 2x - 9x + 3
= 2x ( 3x - 1 ) - 3 ( 3x -1 )
= ( 2x - 3 ) ( 3x -1 )
C2: I = 6x² - 11x + 3
= 6x² - 9x - 2x + 3
= 3x ( 2x - 3 ) - ( 2x - 3 )
= ( 3x - 1 ) ( 2x - 3 )
k ) K = 20x² - 51x + 28
C1: K = 20x² - 51x + 28
= 20x²- 35x- 16x+ 28
= 5x ( 4x - 7 ) - 4 ( 4x - 7 )
= (5x- 4)(4x- 7)
C2: K = 20x² - 51x + 28
= 20x² - 16x -35x + 28
= 4x ( 5x - 4 ) - 7 ( 5x - 4 )
= ( 4x - 7 )( 5x - 4 )
l ) L = 6x² + x - 2
C1: L = 6x² + x - 2
= 6x² + 4x- 3x- 2
= 2x ( 3x + 2 ) - ( 3x + 2 )
= (2x- 1)(3x+ 2)
C2: L = 6x² + x - 2
= 6x² - 3x + 4x - 2
= 3x ( 2x -1 ) + 2 ( 2x - 1 )
= ( 3x + 2 ) ( 2x -1 )
Giải thích các bước giải:
