Question

(2x+3)^2+(x-1)(x+1)=5(x+2)^2-(x-5)(x+1)+(x+4)^2

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Answer 1

\(\left(2x+3\right)^2+\left(x-1\right)\left(x+1\right)=5\left(x+2\right)^2-\left(x-5\right)\left(x+1\right)+\left(x+4\right)^2\)

\(\Leftrightarrow4x^2+12x+9+x^2-1=5\left(x^2+4x+4\right)-\left(x^2+x-5x-5\right)+x^2+8x+16\)

\(\Leftrightarrow4x^2-4x-8=5x^2+20x+20-x^2+4x+5\)

\(\Leftrightarrow-24x=33\)

\(\Leftrightarrow x=-\dfrac{33}{24}\)

Vậy \(S=\left\{-\dfrac{33}{24}\right\}\)