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ginny1029
06-02-2009, 08:11 PM
help lol

if it were just the sqrt's i would square them but I dont know what to do with the first 2's

Subhotosh Khan
06-02-2009, 08:18 PM
help lol

if it were just the sqrt's i would square them but I dont know what to do with the first 2's --- square those too

(2\sqrt{3} )^2 \, = \, 2^2 \cdot (\sqrt{3})^2

I suppose you need to evaluate:

(2\sqrt{3} \, + \, \sqrt{5})\cdot (2\sqrt{3} \, - \, \sqrt{5})

then use

(a + b)\cdot (a-b) \, = \, a^2 \, - \, b^2

ginny1029
06-02-2009, 08:31 PM
ok so how would i write it

(2 sqrt 3)^2 times (sqrt 5)^2

(4 x 3) - (5)

12-5

7

??

Subhotosh Khan
06-02-2009, 08:33 PM
ok so how would i write it

(2 sqrt 3)^2 times (sqrt 5)^2 <<< Why is that???

(4 x 3) - (5)

12-5