Question

Tìm x biết:

1) x² - 10x + 25 = 0

2) 4x² - 9 = 0

Answer 1

1)x^2 - 10x + 25 = 0

X^2-5X-5X+25=0

X(X-5)-5(X-5)=0

(X-5).(X-5)=0

(X-5)^2 =0

X-5=0

X=5

vậy x=5

Answer 2

4x^2 - 9 = 0

4x^2=9

(2x)^2=3^2

2x=3

x=3/2

vậy x=3/2

Answer 3

1 ) \(x^2-10x+25=0\)

\(\Leftrightarrow\left(x-5\right)^2=0\)

\(\Leftrightarrow x-5=0\)

\(\Leftrightarrow x=5\)

Vậy \(x=5\)

2 ) \(4x^2-9=0\)

\(\Leftrightarrow\left(2x\right)^2-3^2=0\)

\(\Leftrightarrow\left(2x-3\right)\left(2x+3\right)=0\)

\(\Leftrightarrow\left[{}\begin{matrix}2x-3=0\\2x+3=0\end{matrix}\right.\Leftrightarrow\left[{}\begin{matrix}2x=3\\2x=-3\end{matrix}\right.\)

\(\Leftrightarrow\left[{}\begin{matrix}x=\dfrac{3}{2}\\x=-\dfrac{3}{2}\end{matrix}\right.\)

Vậy \(\left[{}\begin{matrix}x=\dfrac{3}{2}\\x=-\dfrac{3}{2}\end{matrix}\right.\)