b)
$$\begin{gathered} x^2+6xy + 9y^2-3(x+3y) -4 \\ = {(x+3y)}^2-3(x+3y)-4 \\ = {(x+3y)}^2-4(x+3y) + (x+3y) -4 \\ = (x+3y)(x+3y-4) + (x+3y -4 ) \\ = (x+3y-4)(x+3y+1) \end{gathered}$$

c) $$\begin{gathered} x(x+4)(x+6)(x+10)+128 \\ = \left[x\right(x+10\left)\right] \times \left[\right(x+4\left)\right(x+6\left)\right] + 128 \\ = (x^2+10x)(x^2+10x+24) + 128 \\ = {(x}^{} \end{gathered}$$

2+10x)2+24(x2+10x) + 128= (x2 + 10x)2 + 8(x2+10x) + 16(x2+10x) + 128= (x2+10x + 8)(x2+10x+16)