Question

2, Tìm x biết :

a, \(\frac{x}{4}\) = \(\frac{3}{2}\) 

b, \(\frac{x}{16}=\frac{9}{x}\) 

c, \(\frac{x^2}{6}=\frac{24}{25}\)

d, \(\frac{72-9}{7}=\frac{x-40}{9}\)

Answer 1

a.

\(\frac{x}{4}=\frac{3}{2}\)

\(x=\frac{3}{2}\times4\)

\(x=6\)

b.

\(\frac{x}{16}=\frac{9}{x}\)

\(x\times x=16\times9\)

\(x^2=144\)

\(x^2=\left(\pm12\right)^2\)

\(x=\pm12\)

Vậy \(x=12\) hoặc \(x=-12\)

c.

\(\frac{x^2}{6}=\frac{24}{25}\)

\(x^2=\frac{24}{25}\times6\)

\(x^2=\frac{144}{25}\)

\(x^2=\left(\pm\frac{12}{5}\right)^2\)

\(x=\pm\frac{12}{5}\)

Vậy \(x=\frac{12}{5}\) hoặc \(x=-\frac{12}{5}\)

d.

\(\frac{72-9}{7}=\frac{x-40}{9}\)

\(\frac{x-40}{9}=\frac{63}{7}\)

\(x-40=\frac{63}{7}\times9\)

\(x-40=81\)

\(x=81+40\)

\(x=121\)