Question

[hoàng lan chinh Đỗ]

x.(x+1) - 26 = 30

Answer 1

[Nguyễn Trọng Vũ Hùng]

\(x\cdot\left(x+1\right)-26=30\)

\(x\cdot\left(x+1\right)=30+26\)

\(x\cdot\left(x+1\right)=56\)

\(x\cdot\left(x+1\right)=7\cdot8\)

\(=>x=7\)

Answer 2

[Kiyotaka Ayanokoji]

Trả lời:

\(x.\left(x+1\right)-26=30\)

\(\Leftrightarrow x^2+x-26=30\)

\(\Leftrightarrow x^2+x-56=0\)

\(\Leftrightarrow x^2+8x-7x-56=0\)

\(\Leftrightarrow x.\left(x+8\right)-7.\left(x+8\right)=0\)

\(\Leftrightarrow\left(x+8\right).\left(x-7\right)=0\)

\(\Leftrightarrow\orbr{\begin{cases}x+8=0\\x-7=0\end{cases}\Leftrightarrow}\orbr{\begin{cases}x=-8\\x=7\end{cases}}\)

Vậy \(x\in\left\{-8,7\right\}\)

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