`~rai~`
\(1.(7x+5y)^2\\=(7x)^2+2.7x.5y+(5y)^2\\=49x^2+70xy+25y^2.\\2.(9x-4y)^2\\=(9x)^2-2.9x.4y+(4y)^2\\=81x^2-72xy+16y^2.\\3)25x^2-16y^2\\=(5x)^2-(4y)^2\\=(5x+4y)(5x-4y).\\4)125x^3+8y^3\\=(5x)^3+(2y)^3\\=(5x+2y)[(5x)^2-5x.2y+(2y)^2]\\=(5x+2y)(25x^2-10xy+4y^2).\\5)27x^3-64y^3\\=(3x)^3-(4y)^3\\=(3x-4y)[(3x)^2+3x.4y+(4y)^2]\\=(3x-4y)(9x^2+12xy+16y^2).\\6.(3x+2y)^3\\=(3x)^3+3.(3x)^2.2y+3.3x.(2y)^2+(2y)^3\\=27x^3+54x^2y+36xy^2+8y^3.\)
