Question 63971
The rule for factoring the difference of squares is {{{highlight(a^2-b^2=(a+b)(a-b))}}}
a) x^2  - 100  a=x, b=10
(x+10)(x-10)
:

b) 4y^2  - 49  a=2y, b=7
(2y+7)(2y-7)
:
Happy Calculating!!!