I guess question is to factorise each part
26) (3a)^2- (a^2 - 4)^2= {(3a^2-(a^2-4)} {(3a^2+(a^2-4)
= (2a^2+4)(4a^2-4)
= 2(a^2+2)4(a-2)(a+2)= 8(a^2+2)(a-2)(a+2)
27).=(x-1/x)^2 + 2 -11= (x-1/x)^2 - 9
= (x-1/x - 3)(x-1/x+3)
28).= (2x+1/2x)^2 - 2+1= (2x+1/2x)^2 - (1)^2= (2x+1/2x+1)(2x+1/2x-1)
29).= (2x^2)^2 - (x^2+12x+36)= (2x^2)^2 - (x^2+6)^2= (2x^2+x^2+6)(2x^2-x^2-6)
= (3x^2+6)(x^2-6)= 3(x^2+2)((x-√6)(x+√6)
30). = (b+c){(a^2) - (b+c)^2} = (b+c)(a - b-c)(a + b+c)
