Question

tìm x biết

a) x(x+4)+x+4=0

b) x(x-2)+2-x=0

c) 3x (x-1)-12(x-1)=0

d)x^2 -9=0

e) x^2-3x-10=0

Answer 1

d) x^2-9=0 => x^2=9 => x^2 =3^2 => x =3

Answer 2

Answer 3

Bổ sung thêm cho bạn G-Dragon :)

c, 3x(x - 1) - 12(x - 1) = 0

\(\Leftrightarrow\) (x - 1)(3x - 12) = 0

\(\Leftrightarrow\) (x - 1)(x - 4) = 0

\(\Leftrightarrow\) \(\left[{}\begin{matrix}x-1=0\\x-4=0\end{matrix}\right.\Leftrightarrow\left[{}\begin{matrix}x=1\\x=4\end{matrix}\right.\)

Vậy S = {1; 4}

e, x² - 3x - 10 = 0

\(\Leftrightarrow\) x² - 5x + 2x - 10 = 0

\(\Leftrightarrow\) x(x - 5) - 2(x - 5) = 0

\(\Leftrightarrow\) (x - 5)(x - 2) = 0

\(\Leftrightarrow\) \(\left[{}\begin{matrix}x-5=0\\x-2=0\end{matrix}\right.\Leftrightarrow\left[{}\begin{matrix}x=5\\x=2\end{matrix}\right.\)

Vậy S = {5; 2}

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