Question

how do you factor :
100b^2-64

Answer 1

(10b+8)(10b-8)

Answer 2

The way I do it is I remember this rule i learned a while back.
If you have (perfect square A - perfect square B) it factors into (A's square + B's square)(A's square - B's square)

in your example you have exactly this!
100b^2 is a perfect square because 10b * 10b = 100b^2
64 is also a perfect square because 8 * 8 = 64

So useing the rule above we get (10b + 8)(10b - 8)

Hint* you can always check your answer by expanding it back out.

Answer 3

thanx you helped a lot now i understand! :D