Question

[Trần Minh Thư]

Tìm x, biết:

a, ( \(x\) - \(\dfrac{2}{3}\) )\(^2\) = \(\dfrac{5}{6}\)

b, ( \(\dfrac{3}{4}\) - \(x\) )\(^{^{ }3}\) = -8

Giúp mình vs nhaa, pls

Answer 1

[Nguyễn Huy Tú]

a, \(\left(x-\dfrac{2}{3}\right)^2=\dfrac{5}{6}=\left(\sqrt{\dfrac{5}{6}}\right)^2\)

TH1 : \(x-\dfrac{2}{3}=\sqrt{\dfrac{5}{6}}\Leftrightarrow x=\dfrac{2}{3}+\sqrt{\dfrac{5}{6}}\)

TH2 : \(x-\dfrac{2}{3}=-\sqrt{\dfrac{5}{6}}\Leftrightarrow x=-\sqrt{\dfrac{5}{6}}+\dfrac{2}{3}\)

b, \(\left(\dfrac{3}{4}-x\right)^3=-8=\left(-2\right)^3\Rightarrow\dfrac{3}{4}-x=-2\Leftrightarrow x=\dfrac{3}{4}+2=\dfrac{11}{4}\)