Câu 1:
\(5\left(x-3\right)-3\left(x+1\right)=-12\)
=>\(5x-15-3x-3=-12\)
=>2x-18=-12
=>2x=18-12=6
=>x=6/2=3
Câu 2:
\(7\left(x+9\right)-3\left(5-x\right)=98\)
=>7x+63-15+3x=98
=>10x+48=98
=>10x=98-48=50
=>x=50/10=5
Câu 3:
\(\left(3x-7\right)^3=2^3\cdot3^2+53\)
=>\(\left(3x-7\right)^3=8\cdot9+53=125\)
=>3x-7=5
=>3x=7+5=12
=>\(x=\dfrac{12}{3}=4\)
Câu 4:
\(\left(7x-11\right)^2=2^3\cdot3^2+28\)
=>\(\left(7x-11\right)^2=8\cdot9+28=100\)
=>\(\left[{}\begin{matrix}7x-11=10\\7x-11=-10\end{matrix}\right.\Leftrightarrow\left[{}\begin{matrix}7x=21\\7x=1\end{matrix}\right.\)
=>\(\left[{}\begin{matrix}x=\dfrac{1}{7}\\x=3\end{matrix}\right.\)
Câu 5:
\(26-3\left(2x-3\right)^2=-7^2\)
=>\(3\left(2x-3\right)^2=26+49=75\)
=>(2x-3)2=25
=>\(\left[{}\begin{matrix}2x-3=5\\2x-3=-5\end{matrix}\right.\Leftrightarrow\left[{}\begin{matrix}2x=8\\2x=-2\end{matrix}\right.\)
=>\(\left[{}\begin{matrix}x=4\\x=-1\end{matrix}\right.\)
Câu 6:
\(\left(2x-15\right)^5=\left(2x-15\right)^3\)
=>\(\left(2x-15\right)^5-\left(2x-15\right)^3=0\)
=>\(\left(2x-15\right)^3\left[\left(2x-15\right)^2-1\right]=0\)
=>\(\left(2x-15\right)^3\cdot\left(2x-15-1\right)\left(2x-15+1\right)=0\)
=>\(\left(2x-15\right)^3\cdot\left(2x-16\right)\left(2x-14\right)=0\)
=>\(\left[{}\begin{matrix}2x-15=0\\2x-16=0\\2x-14=0\end{matrix}\right.\Leftrightarrow\left[{}\begin{matrix}x=\dfrac{15}{2}\\x=8\\x=7\end{matrix}\right.\)
