ai muốn chịch mình thì vào đây mình ó cho

My hobby is playing football in spare time. After finishing my homework, I generally spend my lot of free time in playing football. I was so interested in playing football from my childhood and started learning to play well when I was 5 years old. I was in one class when I was 6 years old. My father told my class teacher about my hobby of football. My teacher told him that there is a facility of playing sports daily in the school so he could admit his child. Now, I really enjoy playing football and I participate in the inter-school competitions.

ta có :\(\frac{a}{b}\)=\(\frac{c}{d}\)⇔ad=bc

Vì \(a^2\).(\(c^2\)+\(d^2\))=\(a^2\).\(c^2\)+\(a^2\).\(d^2\)=\(a^2\).\(c^2\)+\(b^2\).\(c^2\)=\(c^2\).(\(a^2\)+\(b^2\))

Vậy \(\left(\frac{a}{c}\right)^2\)=\(\frac{a^2+b^2}{c^2+d^2}\)(đpcm)