If a = (3^1/2 + 2^1/2)^-3 and b = ((3^1/2 - 2^1/2)^-3 then the value of (a+1)^-1 + ( b+1)^-1 is

a)48 root 2

b)50 root 3

c) 1

d) 5

PLZZZZZZZZZZZZZZZZZZ EXPLAIN

Printable View

- June 13th 2013, 12:03 PMsscgeekImportant question plzzzzzzz help
If a = (3^1/2 + 2^1/2)^-3 and b = ((3^1/2 - 2^1/2)^-3 then the value of (a+1)^-1 + ( b+1)^-1 is

a)48 root 2

b)50 root 3

c) 1

d) 5

PLZZZZZZZZZZZZZZZZZZ EXPLAIN - June 13th 2013, 01:31 PMebainesRe: Important question plzzzzzzz help
Not sure if there's an easier way to do this, but if then multiplying it out yields

Similarly

For ease let's use notation and , so that:

Now:

This gets a little messy, but it boils down to:

To finish you just need to sub in the values for x and y and see what you get. - June 13th 2013, 04:09 PMSorobanRe: Important question plzzzzzzz help
Hello, sscgeek!

Quote:

. . .

. . . . . . . . . .

. . . . . . . . . .

. . . . . . . . . .

. . . . . . . . . .

. . . . . . . . . .

. . . . . . . . . .

- June 13th 2013, 08:25 PMIdeaRe: Important question plzzzzzzz help
(a+1)^-1 + ( b+1)^-1 = (a + b + 2) / (a + b + ab +1)

and ab=1 - June 13th 2013, 09:11 PMibduttRe: Important question plzzzzzzz help
- June 13th 2013, 09:15 PMsscgeekRe: Important question plzzzzzzz help
HI BUDDY .CAN U PLZ EXPLAIN HW ab becomes 1

- June 13th 2013, 09:23 PMIdeaRe: Important question plzzzzzzz help
- June 13th 2013, 10:54 PMsscgeekRe: Important question plzzzzzzz help
thanks buddy

- June 13th 2013, 11:38 PMibduttRe: Important question plzzzzzzz help
Remember (a+b)(a-b)=a^2-b^2

Just apply this formula and you will get the result. for we have ab = (9sqrt3)^2-(11sqrt2)^2= 81*3 -121*2=243-242=1

Ok