Question

1 Tìm x

a,(2.x-5)2-(2.x-3)(2x+3)=5

b,(x+3)3-x(x+4)(x-4)=27

c,(3x-2)2-(3x+5)2=4

d, (3x+5)2-(x-3)2=0

Answer 1

a: \(\Leftrightarrow4x^2-20x+25-4x^2+9=5\)

=>-20x+34=5

=>-20x=-29

hay x=29/20

b: \(\Leftrightarrow x^3+9x^2+27x+27-x\left(x^2-16\right)=27\)

\(\Leftrightarrow x^3+9x^2+27x+27-x^3+16x-27=0\)

\(\Leftrightarrow9x^2+43x=0\)

=>x(9x+43)=0

=>x=0 hoặc x=-43/9

c: \(\Leftrightarrow9x^2-12x+4-9x^2-30x-25=4\)

=>-42x-21=4

=>-42x=25

hay x=-25/42

d: \(\Leftrightarrow\left(3x+5+x-3\right)\left(3x+5-x+3\right)=0\)

=>(4x+2)(2x+8)=0

=>x=-1/2 hoặc x=-4