Выросли в 2.5 раза такие вот дела)
1) (2х-5)(2х+5)-4х²=4х²-25-4х²=-25
2) ((х-5у)²-(х+5у)²) : ху=((х-5у-х-5у)*(х-5у+х+5у)) : ху=(-10у * 2х) : ху=
=-20
3) ((3х+2у)²-9х²-4у²) : 6ху=(9х²+12ху+4у²-9х²-4у²) : 6ху=12ху : 6ху=2
4) (4х²+у²-(2х-у)²) : (-2ху)=(4х²+у²-4х²+4ху-у²) : (-2ху)=4ху : (-2ху)=-2
5) (25а²-16)(¹/₅ а+4-¹/₅ а-4)=(25а²-16) * 0=0
6) <u>49х²-9 </u> - 7х =<u>(7х-3)(7х+3)</u> - 7х=7х+3-7х=3
7х-3 7х-3
(5x+y)/(x-5y) + (5x-y)/(x+5y)÷(x²+y²)/(x²-25y²)=
=[(5x+y)(x+5y) + (5x-y)(x-5y)]/(x²+y²)<span>÷(x²+y²)/(x²-25y²)=
=[5x</span>²+25xy+5y²+xy+5x²+xy-25xy+5y²](x²-25y²)/(x²+y²)(x²-25y²)=
=сокращаем, получаем=
=(10x²+10y²)/(x²+y²)=10<span>(x²+y²)/(x²+y²)</span>=10