①(5+3a)^2
=25+30x+9x²
②(2x-7y)^2
=4x²-28xy+49y²
③(-2a-5)^2
=4x²+20x+25
④(-xy+1)^2
=x²y²-2xy+1
⑤(-xy-1)^2
=x²y²+2xy+1