8x2+30x+7=0
8x2+16x+14x+7=0
8x(x+2) +7(x+2)=0
(8x+7)(x+2)=0
=>\(\orbr{\begin{cases}8x+7=0\\x+2=0\end{cases}\Rightarrow\orbr{\begin{cases}x=-\frac{7}{8}\\x=-2\end{cases}}}\)
a)
4x2-8x+4=2(1-x)(x+1)
4x2-8x+4-2+2x2=0
6x2-8x+2=0
2(3x2-4x+1)=0
3x2-3x-x+1=0
3x(x-1) -(x-1)=0
(3x-1)(x-1)=0
\(\Rightarrow\orbr{\begin{cases}3x-1=0\\x-1=0\end{cases}\Rightarrow\orbr{\begin{cases}x=\frac{1}{3}\\x=1\end{cases}}}\)
d,
x2+3x-18=0
=> x2-3x+6x-18=8
=> x(x-3)+6(x-3)=0
=> (x-3)(x+6)=0
=> \(\orbr{\begin{cases}x=3\\x=-6\end{cases}}\)
a, \(4x^2-8x+4=2\left(1-x\right)\left(x+1\right)\)
\(\Leftrightarrow-4x+4=2-2x^2\Leftrightarrow x=1\)
b, \(4x^2-25-\left(2x-5\right)\left(2x+7\right)=0\)
\(\Leftrightarrow4x^2-4x+35-4x^2-25=0\Leftrightarrow x=\frac{5}{2}\)
c, \(8x^2+30x+7=0\Leftrightarrow\left(x+\frac{1}{4}\right)\left(x+\frac{7}{2}\right)=0\Leftrightarrow x=-\frac{1}{4};-\frac{7}{2}\)
d, \(x^2+3x-18=0\Leftrightarrow\left(x-3\right)\left(x+6\right)=0\Leftrightarrow x=3;-6\)
