a) \(\left(a^2-4\right)\left(a^2+4\right)=a^4-16\)
b) \(\left(x^3-3y\right)\left(x^3+3y\right)=x^6-9y^2\)
c) \(\left(a-b\right)\left(a+b\right)\left(a^2+b^2\right)\left(a^4+b^4\right)=\left(a^2-b^2\right)\left(a^2+b^2\right)\left(a^4+b^4\right)=\left(a^4-b^4\right)\left(a^4+b^4\right)=a^8-b^8\)
d) \(\left(a-b+c\right)\left(a+b+c\right)=\left[\left(a+c\right)-b\right]\left[\left(a+c\right)+b\right]=\left(a+c\right)^2-b^2=a^2-b^2+c^2+2ac\)
e) \(\left(x+2-y\right)\left(x-2-y\right)=\left[\left(x-y\right)+2\right]\left[\left(x-y\right)-2\right]=\left(x-y\right)^2-4=x^2+y^2-2xy-4\)
a. a4 - 16
b. x6 - 9y2
c. (a2 - b2)(a4 - b4)
d. a2 - (b + c)2
e. x2 - (2 - y)2
