Question

Tìm x :

3(x+5) -3 = 2(x+1) +7

15-(x+2)² = -1

75-(2x+1)³ =11

Answer 1

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⇒\(\left[{}\begin{matrix}2x+1=8\\2x+1=-8\end{matrix}\right.\)⇒\(\left[{}\begin{matrix}x=3,5\\x=-4,5\end{matrix}\right.\)

Answer 2

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 \(\left(x+2\right)^2=16\)

\(\Leftrightarrow\left[{}\begin{matrix}x+2=4\\x+2=-4\end{matrix}\right.\Leftrightarrow\left[{}\begin{matrix}x=2\\x=-6\end{matrix}\right.\)

Answer 3

c) Ta có: \(75-\left(2x+1\right)^3=11\)

\(\Leftrightarrow2x+1=4\)

hay \(x=\dfrac{3}{2}\)