a) \(9\left(a+b\right)^2-\left(a+b\right)=\left(a+b\right)\cdot9\cdot\left(a+b-1\right)\)
b)\(\left(mx+my\right)+\left(3x+3y\right)=m\left(x+y\right)+3\left(x+y\right)=\left(m+3\right)\left(x+y\right)\)
c) \(\left(12xy-6x\right)-\left(2y-1\right)=6x\left(2y-1\right)-\left(2y-1\right)=\left(6x-1\right)\left(2y-1\right)\)
d) \(\left(7xy^2-5x^2y\right)+\left(5x-7y\right)=xy\left(7y-5x\right)+\left(5x-7y\right)=xy\left(7y-5x\right)-\left(7y-5x\right)=\left(xy-1\right)\left(7y-5x\right)\)
a: \(9\left(a+b\right)^2-\left(a+b\right)=\left(a+b\right)\left(9a+9b-1\right)\)
b: \(\left(mx+my\right)+\left(3x+3y\right)=\left(x+y\right)\left(m+3\right)\)
c: \(\left(12xy-6x\right)-\left(2y-1\right)=\left(2y-1\right)\left(6x-1\right)\)
d: \(\left(7xy^2-5x^2y\right)+\left(5x-7y\right)=\left(7x-5y\right)\left(xy-1\right)\)