find the roots of the equasions

Question

factorise the following equasion and find the roots of the equasion ?

x2-81

Answer 1

x^2 - 81 is a perfect square.

x^2 - 81 = 0

bring over -81 (but change the sign)

x^2 = 81

then take the square root of 81.  when you do this, you will get one answer; however, you must take both the positive and negative value (because it is a perfect square)

sqrt 81 = 9

therefore x = 9, x = -9