\(2x^2-7x-15=22.\)
\(\Leftrightarrow2x^2-7x-37=0.\)
\(\Leftrightarrow x^2-\frac{7}{2}x-\frac{37}{2}=0.\)
\(\Leftrightarrow x^2-2.\frac{7}{4}x+\frac{49}{16}-\frac{49}{16}-\frac{37}{2}=0.\)
\(\Leftrightarrow\left(x-\frac{7}{4}\right)^2=\frac{345}{16}.\)
\(\Leftrightarrow\orbr{\begin{cases}x-\frac{7}{4}=\frac{\sqrt{345}}{4}\\x-\frac{7}{4}=-\frac{\sqrt{345}}{4}\end{cases}}\)
\(\Leftrightarrow\orbr{\begin{cases}x=\frac{\sqrt{345}+7}{4}\\x=\frac{-\sqrt{345}+7}{4}\end{cases}}\)
Học tốt
(2x+3)(x-5)=42+6
2x2-10x+3x-15x=16+6
2x2-7x-15=22
2x2-7x-15-22=0
2x2-7x-37=0
\( {7 \pm\sqrt{345} \over 2}\)\(+{7 - \sqrt{345} \over 2}\)=0
x1=-2,89354
x2=6,39354
neu co sai cho to xin loi
chuc ban hoc tot
