Question

因为（根号a+根号b)（根号a- 根号b)=a - b

Answer 1

(1)

1/√2+1=（√2-1）/（√2+1)（√2-1）=√2-1,

1/(√3+√2)=(√3-√2)/(√3+√2)(√3-√2)=√3-√2

.

1/(√2009+√2008)=(√2009-√2008)/(√2009+√2008)(√2009-√2008)=√2009-√2008

所以 原式=(√2009-1)(√2009+1)=2009-1=2008

(2)

3/(4-√13)=3(4+√13)/(4-√13)(4+√13)=3(4+√13)/3=4+√13

同理 6/(√13-√7)=√13+√7 2/(3+√7)=3-√7

所以 原式=4-3=1