\(a,25x^5y^4-10x^3y^4\\ =5x^3y^4\cdot5x^2-5x^3y^4\cdot2\\ =5x^3y^4\left(5x^2-2\right)\\ b,x+1+\left(x^2+2x+1\right)\\ =\left(x+1\right)+\left(x+1\right)^2\\ =\left(x+1\right)\left(1+x+1\right)\\ =\left(x+1\right)\left(x+2\right)\\ c,?\\ d,a^4-16\\ =\left(a^2\right)^2-4^2\\ =\left(a^2-4\right)\left(a^2+4\right)\\ =\left(a-2\right)\left(a+2\right)\left(a^2+4\right)\\ e,5x^2-5xy-x+y\\ =5x\left(x-y\right)-\left(x-y\right)\\ =\left(x-y\right)\left(5x-1\right)\\ f,5x^2+10xy+5y^2\\ =5\left(x^2+2xy+y^2\right)\\ =5\left(x+y\right)^2\\ g,5x^4y^2+20x^3y^2+20x^2y^2\\ =5x^2y^2\left(x^2+4x+4\right)\\ =5x^2y^2\left(x+2\right)^2\\ h,\left(a^2+4\right)^2-16a^2\\ =\left(a^2+4\right)^2-\left(4a\right)^2\\ =\left(a^2-4a+4\right)\left(a^2+4a+4\right)\\ =\left(a-2\right)^2\left(a+2\right)^2\)
