Cho a/b = c/d. (b, c, d khác 0; c + d khác 0). Chứng minh: (a * b)/(c * d) = (a + b)^2/(c + d)^2

$$\begin{gathered} \mathrm{Câu} 1: \mathrm{Cho} \frac{\mathrm{a}}{\mathrm{b}} =\frac{\mathrm{c}}{\mathrm{d}} \\ (\mathrm{b},\mathrm{c},\mathrm{d} \mathrm{khác} 0; \mathrm{c} + \mathrm{d} \mathrm{khác} 0) \\ \mathrm{Chứng} \mathrm{minh} \frac{\mathrm{a}.\mathrm{b}}{\mathrm{c}.\mathrm{d}} = \frac{{( \mathrm{a} + \mathrm{b})}^2}{{( \mathrm{c} + \mathrm{d})}^2} \\ \mathrm{ai} \mathrm{nhanh} 5\mathrm{đ}😇 \end{gathered}$$