bài 1 thực hiện phép tính nhân
a, (x-1)(x+2)(x-1)
b,(x-7)(x+6)
c,(x+4)(x+5)(x+1)(x-2)
d,(x+5)(x+7)
e,(x-6)(x+3)(x+4)
bài 1 thực hiện phép tính nhân a, (x-1)(x+2)(x-1) b,(x-7)(x+6) c,(x+4)(x+5)(x+1)(x-2) d,(x+5)(x+7) e,(x-6)(x+3)(x+4)
By Aaliyah
By Aaliyah
bài 1 thực hiện phép tính nhân
a, (x-1)(x+2)(x-1)
b,(x-7)(x+6)
c,(x+4)(x+5)(x+1)(x-2)
d,(x+5)(x+7)
e,(x-6)(x+3)(x+4)
a, (x-1)(x+2)(x-1)
= (x-1)(x-1)(x+2)
=(x-1)²(x+2)
=(x² – 2x + 1)(x+2)
= x³ + 2x² – 2x² – 4x + x + 2
= x³ -3x + 2
b,(x-7)(x+6)
= x² + 6x – 7x – 42
= x² – x – 42
c,(x+4)(x+5)(x+1)(x-2)
=(x² + 5x + 4x + 20)(x+1)(x-2)
= (x² + 9x + 20)(x+1)(x-2)
= (x³ + x² + 9x² +9x + 20x +20)(x-2)
=(x³ + 10x² + 29x + 20)(x-2)
= x^4 – 2x³ + 10x³ – 20x² + 29x² – 58x + 20x – 40
= x^4 + 8x³ + 9x² – 38x – 40
d,(x+5)(x+7)
= x² + 7x + 5x + 35
= x² + 12x + 35
e,(x-6)(x+3)(x+4)
= (x² + 3x – 6x – 18)(x+4)
= x³ + 4x² + 3x² + 12x -6x² – 24x – 18x – 72
= x³ + x² – 30x – 72