Question

b;x(x-1)(x+1)(x+2)-24 =

c; ( x+2)(x-2)(x²-10)-72=

d; (x-7)(x-5)(x-4)(x-2)-72=

mọi ngời giúp mình vs nha

Answer 1

b​; x(x-1)(x+1)(x+2)-24

=(x²+x)(x²+x-2)-24

​Đ​ặt x²​+x=k khi đ​ó​ k(k-2)-24=k²-2k-24

​=(k²-2k+1)-25=(k-1)²-5²

​ =(k-1-5)(k-1+5)=(k-6)(k+4)

c; (x+2)(x-2)(x²-10)-72

​ =(x²-4)(x²-10)-72

​Đ​ặt x²​-7=k khi đ​ó​ (k-3)(k+3)-72=k²-9-72

=k²-81=(k-9)(k+9)=(x²-7-9)(x²-7+9)

=(x²-16)(x^​2+2)=(x-4)(x+4)(x²+2)

d; (x-7)(x-5)(x-4)(x-2)-72

=(x²-9x+14)(x²-9x+8)-72

Đ​ặt x²-9x​+11=k khi đ​ó​ (k+3)(k-3)-72=k²-9-72

=k²-81=(k-9)(k+9)=(x²-9x+11-9)(x²-9x+11+9)

=(x²-9x+2)(x²-9x+20)

=(x²-9x+2)(x²-4x-5x​+20)

=(x²-9x+2)(x-4)(x-5)