Question

tìm x thuộc Q biết: \(\left(2.x+3\right)^2=16\)

Answer 1

\(\left(2x+3\right)^2=16\)

\(\Leftrightarrow\left[{}\begin{matrix}2x+3=\sqrt{16}\\2x+3=-\sqrt{16}\end{matrix}\right.\) \(\Leftrightarrow\left[{}\begin{matrix}2x+3=4\\2x+3=-4\end{matrix}\right.\) \(\Leftrightarrow\left[{}\begin{matrix}x=\dfrac{1}{2}\\x=-\dfrac{7}{2}\end{matrix}\right.\)

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Answer 2

(2x + 3)² = 16

⇔ (2x + 3 )² = 4² hoặc (2x + 3 )² = (-4)²

⇔ 2x + 3 = 4 hoặc 2x + 3 = -4

⇔ 2x = 1 hoặc 2x = -7

⇔ x = \(\dfrac{1}{2}\) hoặc x = \(\dfrac{-7}{2}\)

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