a. \(\left(2x-\dfrac{1}{2}\right)^3-15=12\)
<=> (2x)3 - 3.(2x)2.\(\dfrac{1}{2}\) + 3.2x.\(\left(\dfrac{1}{2}\right)^2\) - \(\left(\dfrac{1}{2}\right)^3\) - 15 = 12
<=> 8x3 - 3x2 + 1,5x - \(\dfrac{1}{8}\) = 27
<=> 8x3 - 3x2 + 1,5x = 27,125
Phần này mik cắt vì dài nên mik ra kết quả luôn, mong bn thông cảm.
<=> x = 1,593163631 \(\approx\) 1,59
a: Ta có: \(\left(2x-\dfrac{1}{2}\right)^3-15=12\)
\(\Leftrightarrow\left(2x-\dfrac{1}{2}\right)^3=27\)
\(\Leftrightarrow2x-\dfrac{1}{2}=3\)
\(\Leftrightarrow2x=\dfrac{7}{2}\)
hay \(x=\dfrac{7}{4}\)
b: Ta có: \(45-\left(1-\dfrac{x}{3}\right)^2=-4\)
\(\Leftrightarrow\left(\dfrac{1}{3}x-1\right)^2=49\)
\(\Leftrightarrow\left[{}\begin{matrix}\dfrac{1}{3}x-1=7\\\dfrac{1}{3}x-1=-7\end{matrix}\right.\Leftrightarrow\left[{}\begin{matrix}\dfrac{1}{3}x=8\\\dfrac{1}{3}x=-6\end{matrix}\right.\Leftrightarrow\left[{}\begin{matrix}x=24\\x=-18\end{matrix}\right.\)
