3(x+5) -3 = 2(x+1) +7
⇒3x+15-3=2x+2+7
⇒3x+12=2x+9
⇒x=-3
15-(x+2)² = -1
⇒(x+2)2=16
⇒\(\left[{}\begin{matrix}x+2=4\\x+2=-4\end{matrix}\right.\)
⇒\(\left[{}\begin{matrix}x=2\\x=-6\end{matrix}\right.\)
75-(2x+1)³ =11
⇒(2x+1)³=64⇒\(\left[{}\begin{matrix}2x+1=8\\2x+1=-8\end{matrix}\right.\)⇒\(\left[{}\begin{matrix}x=3,5\\x=-4,5\end{matrix}\right.\)
a) ta có: 3(x+5)-3=2(x+1)+7
nên 3x-2x=2+7-15+3
hay x=-3
b) Ta có: \(15-\left(x+2\right)^2=-1\)
nên \(\left(x+2\right)^2=16\)
\(\Leftrightarrow\left[{}\begin{matrix}x+2=4\\x+2=-4\end{matrix}\right.\Leftrightarrow\left[{}\begin{matrix}x=2\\x=-6\end{matrix}\right.\)
c) Ta có: \(75-\left(2x+1\right)^3=11\)
\(\Leftrightarrow2x+1=4\)
hay \(x=\dfrac{3}{2}\)
