Question

Tìm \(x\), biết :

 a) \(\dfrac{x}{-15}=-\dfrac{60}{x}\)

b) \(-\dfrac{2}{x}=-\dfrac{x}{\dfrac{8}{25}}\)

Answer 1

a) \(x^2=\left(-15\right).\left(-60\right)=900=>x=\)\(\pm\)\(30\)

b) \(-x^2=\dfrac{-16}{25}=>x^2=\dfrac{16}{25}=>x=\)\(\pm\)\(\dfrac{4}{5}\)

Answer 2

a)\(\dfrac{x}{-15}\)= \(-\dfrac{60}{x}\)

=> x . x = -15 . (-60)

=> \(^{x^2}\) = 900

x = 30

b) \(-\dfrac{2}{x}\) = \(-\dfrac{x}{\dfrac{8}{25}}\)

=> -2 . \(\dfrac{8}{25}\) = x . (-x)

=> \(\dfrac{-16}{25}\) = \(^{x^2}\)

=> x = \(\dfrac{4}{5}\)và \(-\dfrac{4}{5}\)

nhớ tích cho mk vs nha >_<

Answer 3

a) \(\frac{x}{-15}=\frac{-60}{x}\)

==> x.x =-15.(-60)

\(^{x^2}\)= 900

==> x= 30 hoặc x= -30

b) \(-\frac{2}{x}=\frac{-x}{\frac{8}{25}}\)

- \(x^2\)= \(\frac{-16}{25}\)

\(^{x^2}\)=\(\frac{16}{25}=\left(\frac{4}{5}\right)^2=\left(\frac{-4}{5}\right)^2\)

==> x =\(\frac{4}{5}\) hoặc x = \(\frac{-4}{5}\)