Question

Tìm x

a)(2x+1)²-4(x+2)² =9

b)(3x-1)² +2(x+3)² +11(x+1)(1-x)=6

c)(x+1)³ - x² (x+3)=2

d)(x-2)³ -x(x+1)(x-1)+6x² =5

e)(x-3)(x² +3x +9)-x(x+4)(x-4)=5

g)(x-2)³ -(x+5)(x² -5x+25)+6x² =11

Answer 1

a: \(\Leftrightarrow4x^2+4x+1-4x^2-16x-16=9\)

=>-12x-15=9

=>-12x=24

hay x=-2

b: \(\Leftrightarrow9x^2-6x+1+2x^2+12x+18+11\left(1-x^2\right)=6\)

\(\Leftrightarrow11x^2+6x+19+11-11x^2=6\)

=>6x+30=6

=>6x=-24

hay x=-4

c: \(\Leftrightarrow x^3+3x^2+3x+1-x^3-3x^2=2\)

=>3x=1

hay x=1/3

d: \(\Leftrightarrow x^3-6x^2+12x-8-x\left(x^2-1\right)+6x^2=5\)

\(\Leftrightarrow x^3+12x-8-x^3+x=5\)

=>13x=13

hay x=1

e: \(\Leftrightarrow x^3-27-x^3+16x=5\)

=>16x=32

hay x=2