Question

помогите решить 1, 4

Answer 1

$\boxed{a^2-b^2=(a-b)(a+b)}\\\\\displaystyle\sf \frac{38^2-28^2}{47^2-19^2}=\frac{(38-28)(38+28)}{(47-19)(47+19)} =\frac{10\cdot 66}{28\cdot 66}=\frac{10}{28}=\frac{5}{14}\\\\\frac{200^2-380^2}{420^2-160^2} =\frac{(200-380)(200+380)}{(420-160)(420+160)}=\frac{-180\cdot 580}{260\cdot 580}=-\frac{180}{260}=-\frac{9}{13}$