F.2Maths30p!!!!!!

1)When a number is either corrected to 2 sig. fig. or3 sig. fig.,the results are the same. write down the no.
1203 is such a number.
Corrected to 2 or 3 significant digits, the number is rounded off to 1200.
Another example is 75973 which will be rounded to 76000
2)suggest 2 ways of factorizing x6 – y6
First way : x6 – y6
= (x3)2 – (y3)2
= (x3 + y3)(x3 – y3)
= (x + y)(x2 – xy + y2)(x – y)(x2 + xy + y2)
Second way : x6 – y6
= (x2)3 – (y2)3
= (x2 – y2)(x4 + x2y2 + y4)
= (x – y)(x + y)[x4 + 2x2y2 + y4 – x2y2]
= (x – y)(x + y)[(x2 + y2)2 – (xy)2]
= (x – y)(x + y)[(x2 + xy + y2)(x2 – xy + y2) final result is the same

一、0
二、(x^3+y^3)(x^3-y^3)；(x^2-y^2)[x^4+(xy)^2+y^4]