Question

3, Tìm x, biết

d) \(\dfrac{-16}{x}=\dfrac{x}{-4}\)

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

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

Answer 1

3, Tìm x, biết

\(d,\dfrac{-16}{x}=\dfrac{x}{-4}=>x^2=\left(-16\right).\left(-4\right)=>x^2=64\)

\(=>x=8\) hay \(x=-8\)

\(e,\dfrac{x}{-2}=\dfrac{\dfrac{8}{25}}{-x}=>-x^2=-2.\dfrac{8}{5}=\dfrac{-16}{25}\)

\(=>-x^2=0,64=>x=0,8\)

\(g,\dfrac{x}{-15}=\dfrac{-60}{x}\)

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

Answer 2

d) \(\dfrac{-16}{x}=\dfrac{x}{-4}\)

= 16 . 4 = x.x

= 64 = \(x^2\)

= \(8^2=x^2\)

vậy x = 8

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

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

= -0,64 = \(-x^2\)

= 0,64 = \(x^2\)

0,8\(^2=x^2\)

vậy x = 0,8

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

= -15 . -60 = x.x

= 900 = \(x^2\)

30 \(^2=x^2\)

vậy x = 30