( 15x^2 + 6y )^2 = ( 3^( 5x^2 + 2y ))^2 = 9( 5x^2 + 2y )^2
9x^2 - 48xy + 64y^2 = ( 3x - 8y )^2
1)...=(2x-5y)^2-(2x-5y)=( 2x-5y)(2x-5y-1)
2)...=(3x-7y)^2+2(3x-7y)=(3x-7y)(3x-7y+2)
3)...=x^2-(3y-5z)^2= (x-3y+5z)(x+3y-5z)
4)...=81x^2-(2y+6z)^2=(9x-2y-6z)(9x+2y+6z)