Question

Tìm x

a) x^2-25-(x+5)=0

b)(2x-1)^2-(4x^2-1)=0

c) x^2(x^2+4)-x^2-4+0

Answer 1

Tìm x:

a) \(x^2-25-\left(x+5\right)=0\)

\(\Leftrightarrow x^2-x-30=0\)

\(\Leftrightarrow\)\(\left[\begin{array}{} x=6\\ x=-5 \end{array} \right.\)

b) \(\left(2x-1\right)^2-\left(4x^2-1\right)=0\)

\(\Leftrightarrow4x^2-4x+1-4x^2+1=0\)

\(\Leftrightarrow2-4x=0\)

\(\Leftrightarrow x=\dfrac{1}{2}\)

c) \(x^2\left(x^2+4\right)-x^2-4=0\)

\(\Leftrightarrow x^2\left(x^2+4\right)-\left(x^2+4\right)=0\)

\(\Leftrightarrow\left(x^2-1\right)\left(x^2+4\right)=0\)

\(\Leftrightarrow\)\(\left[\begin{array}{} x^2-1=0\\ x^2+4=0 \end{array} \right.\)

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