Question

phan tich da thuc thanh nhan tu

a, x^5+x-1

b, (x^2+3x+2)(x62+7x+12)-24 

Answer 1

b ( x^2 + 3x + 2)( x^2 + 7x + 12) - 24 

= [ x^2 +x + 2x + 2) ( x^2 +3x + 4x + 12) - 24

= [x(x+1) + 2 (x + 1) [x(x+3) + 4(x+3) ] - 24

= ( x + 1)(x+2) (x+3)(x+4) - 24

= ( x + 1).(x+4) (x+2)(x+3) - 24

=(x^2 + 5x + 4)(x^2+5x+6) - 24 

Đặt x^2 + 5x +4 =y ta có:

= y(y+2) - 24

= y^2 + 2y - 24 

= y^2 + 2y + 1 - 25 

= ( y + 1)^2 - (5)^2 

= ( y + 1 - 5 )( y + 1 + 5)

= ( y- 4)(y +6) 

Thay y trở lại là đc 

đúng nha