a)пусть одна сторона=x, тогда вторая=y=1,1x
1,1x+x=126
2.1x=126
x=60
1,1x=60*1,1=66
4у+7/2у-3-у-3/2у+3=1
5у=1
у=1/5
[√(n+2)*(√(n+2)+√(n-2))]/[√(n+2)*(√(n+2)-√(n-2))] +
+[√(n+2)*(√(n+2)-√(n-2))]/[√(n+2)*(√(n+2)+√(n-2))]=
=(√(n+2)+√(n-2))/(√(n+2)-√(n-2))+(√(n+2)-√(n-2))/(√(n+2)+√(n-2))=
(n+2+2√(n²-2)+n-2+n+2-2√(n²-2)+n-2)/[(√(n+2)+√(n-2))(√(n+2)-√(n-2))]=
=4n/(n+2-n+2)=4n/4=n
√(√2-1)²+2-√2=√2-1+2-√2=1
(cos^2a - sin^2a)(cos^2a + sin^2a) - cos^2a =
= (cos^2a - sin^2a)*1 - cos^2a =
= cos^2a - sin^2a - cos^2a =
= - sin^2a