\(63x^2-65x-8=0\)
Ta có: \(\Delta=65^2+4.8.63=6241\)
Vậy pt có 2 nghiệm:
\(x_1=\frac{65+\sqrt{6241}}{126}\);\(x_2=\frac{65-\sqrt{6241}}{126}\)
\(63x^2-65x-8=0\)
\(63x^2-72x+7x-8=0\)
\(9x\cdot\left(7x-8\right)+7x-8=0\)
\(\left(7x-8\right)\cdot\left(9x+1\right)=0\)
\(\orbr{\begin{cases}7x-8=0\\9x+1=0\end{cases}\Rightarrow\orbr{\begin{cases}x=\frac{8}{7}\\x=-\frac{1}{9}\end{cases}}}\)
\(63x^2-65x-8=0\)
\(63x^2-72x+7x-8=0\)
\(9x\left(7x-8\right)+7x-8=0\)
\(\left(7x-8\right).\left(9x+1\right)=0\)
\(\Rightarrow\orbr{\begin{cases}7x-8=0\\9x+1=0\end{cases}\Rightarrow\orbr{\begin{cases}7x=8\\9x=-1\end{cases}\Rightarrow}\orbr{\begin{cases}x=\frac{8}{7}\\x=-\frac{1}{9}\end{cases}}}\)
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