Ответ: 1. 81а^2+(9ab+9ab)+b^2= (9a+b)^22. 25a^2-(35ab+35ab)+49b^2=(5a-7b)^23. 100x^2y^2-(10xy+10xy)+1=(10xy-1)^24. 9c^2+(12cd +12cd)+16d^2=(3c+4d)^25. 49x^2+(14xy+14xy)+4y^2=(7x+2y)^26. 16 — (4a^2b^2+4a^2b^2)+a^4b^4=(4-a^2b^2)^2