Question

how many numbers lie between 10 and 300 , which when divisible by 4 leaves a remainder 3

Answer 1

12,16,20_____________ 294
a=12
d=16-12
=4

Answer 2

take 3x common factor out of the bracket.

factorise (x^{4}  - 16) as (x^{2}  + 4)(x^{2}  - 4)

further factorise (x^{2}  - 4) as (x+2)(x-2)