factor this xsquared-49

Question

psymon · Answer

ANYTHING that is something minus something else can be factored in this specific way. Now with your problem it just comes outto be very pretty, but just to let you know that this can always be done in some way if you have a subtraction of two things. 
This is what is called a difference of squares and it factors like this:
$$a ^{2}-b ^{2}=(a-b)(a+b)$$So all you need to know is what is the square root of x^2 and what is the square root of 49. After that, you just plug them into that formula.

anonymous · Answer

ok

anonymous · Answer

what is the factor of this 81-ysquared

akashdeepdeb · Answer

Just as @Psymon said!
81-ysquared
is
(9-y)(9+y).
Understood? :)