How do you factor a^8 - a^2b^6a8a2b6?

1 Answer
May 10, 2016

a^2(a-b)(a^2+ab+b^2)(a+b)(a^2-ab+b^2)a2(ab)(a2+ab+b2)(a+b)(a2ab+b2)

Explanation:

a^(2+6) - a^2b^6 a2+6a2b6

= a^2a^6-a^2b^6=a2a6a2b6

=a^2(a^6-b^6)=a2(a6b6), here color(red)(a^2)a2 is common between the terms

=a^2(a^(3xx2)-b^(3xx2))=a2(a3×2b3×2)

=a^2[(a^3)^2-(b^3)^2]=a2[(a3)2(b3)2]

color(red)("This is of the form " x^2-y^2 = (x-y)(x+y), "where " x=a^3 " and " y = b^3)This is of the form x2y2=(xy)(x+y),where x=a3 and y=b3

=a^2(a^3-b^3)(a^3+b^3)=a2(a3b3)(a3+b3)

Now we factorize (a^3-b^3)(a3b3) and (a^3+b^3)(a3+b3):

color(red)("We know that " (a^3-b^3)=(a-b)(a^2+ab+b^2)We know that (a3b3)=(ab)(a2+ab+b2)

color(red)("And "(a^3+b^3)=(a+b)(a^2-ab+b^2)And (a3+b3)=(a+b)(a2ab+b2)

Then,

a^2(a^3-b^3)(a^3+b^3)=color(blue)(a^2(a-b)(a^2+ab+b^2)(a+b)(a^2-ab+b^2)a2(a3b3)(a3+b3)=a2(ab)(a2+ab+b2)(a+b)(a2ab+b2)