Question

a,2x(x+5)=(x+3)²+(x-1)²+20

b,(2x-2)²=(x+1)²+3(x-2)(x+5)

c,(x-1)²+(x+3)²=2(x-2)(x+1)+38

d,(x+2)³-(x-2)³=12x(x-1)-8

Answer 1

Nhiều câu quá >.<

a/ \(2x\left(x+5\right)=\left(x+3\right)^2+\left(x-1\right)^2+20.\)

\(2x^2+10x=x^2+6x+9+x^2-2x+1+20.\)

\(10x=4x+30\)

\(6x=30\Rightarrow x=5\)

các câu còn lại tương tự

Answer 2

\(a,2x\left(x+5\right)=\left(x+3\right)^2+\left(x-1\right)^2+20\)

\(\Leftrightarrow2x^2+10x=x^2+6x+9+x^2-2x+1+20\)

\(\Leftrightarrow2x^2+10x=2x^2+4x+30\)

\(\Leftrightarrow2x^2+10x-2x^2-4x=30\)

\(\Leftrightarrow6x=30\)

\(\Leftrightarrow x=5\)

Vậy ...........

\(b,\left(2x-2\right)^2=\left(x+1\right)^2+3\left(x-2\right)\left(x+5\right)\)

\(\Leftrightarrow4x^2-8x+4=x^2+2x+1+3x^2+15x-6x-30\)

\(\Leftrightarrow4x^2-8x+4=4x^2+11x-29\)

\(\Leftrightarrow4x^2-8x-4x^2-11x=-29-4\)

\(\Leftrightarrow-19x=-33\)

\(\Leftrightarrow x=\frac{33}{19}\)

Vậy...........

\(c,\left(x-1\right)^2+\left(x+3\right)^2=2\left(x-2\right)\left(x+1\right)+38\)

\(\Leftrightarrow x^2-2x+1+x^2+6x+9=2x^2+2x-4x-4+38\)

\(\Leftrightarrow2x^2+4x+10=2x^2-2x+34\)

\(\Leftrightarrow2x^2+4x-2x^2+2x=34-10\)

\(\Leftrightarrow6x=24\)

\(\Leftrightarrow x=4\)

Vậy.............

\(d,\left(x+2\right)^3-\left(x-2\right)^3=12x\left(x-1\right)-18\)

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

\(\Leftrightarrow x^3+6x+12x+8-x^3+6x-12x+8=12x^2-12x-8\)

\(\Leftrightarrow12x=-24\)

\(\Leftrightarrow x=-2\)

Vậy............