Metoda 1(substituție)
[tex] \frac{a}{b}= \frac{5}{2} \\ a= \frac{5b}{2} \\ 4a^2+25b^2=4( \frac{5b}{2})^2+25b^2=4* \frac{25b^2}{4}+25b^2=50b^2= \frac{5b}{2}*20b=20ab [/tex] (Adevărat)
Metoda 2(mai deșteaptă)
[tex] \frac{a}{b}= \frac{5}{2} \\ 2a=5b \\ 4a^2+25b^2=20ab \\ 4a^2-20ab+25b^2=0 \\ (2a-5b)^2=0 \\ 2a-5b=0 \\ 2a=5b [/tex]
(Adevărat)
