Question

Bài 1: Tìm x biết

a) x. ( x+4) . ( 4 - x ) + ( x-5 ) . ( x2 +5x + 25 ) = 3

b) ( x+1 )3 - ( x-1 )3 - 6 . ( x-1 )2 = -10

c) ( x-3 ) . ( x2 + 3x + 9 ) + x. ( x+2 ) . ( 2-x ) = 1

Làm nhanh giùm mình nha

Answer 1

a: \(\Leftrightarrow x\left(16-x^2\right)+x^3-125=3\)

=>16x-125=3

=>16x=128

hay x=8

b: \(\Leftrightarrow x^3+3x^2+3x+1-x^3+3x^2-3x+1-6\left(x^2-2x+1\right)=-10\)

\(\Leftrightarrow6x^2+2-6x^2+12x-6=-10\)

=>12x-4=-10

=>12x=-6

hay x=-1/2

c: \(\Leftrightarrow x^3-27+x\left(4-x^2\right)=1\)

\(\Leftrightarrow4x-27=1\)

hay x=7