Expert: Sherman D. - 1/23/2005

Question
"I'm confused about these three problems, they're similar but I cannot figure them out.

1. 3 sqrt(-50) + sqrt(-72)

2.[-4 +sqrt(-20)]/2

3. [7 sqrt(-2)][-4 sqrt(-3]";  

Answer
I will give you a real good mathematical explaination

you might be asking your self what to do with the -, well the sqrt of a negative, or the sqrt of a -1, is "i", so here is what you do

1.)
3sqrt(-50) + sqrt(-72)
3sqrt(-25 * 2) + sqrt(-36 * 2)
(3 * 5i)sqrt(2) + 6isqrt(2)
15isqrt(2) + 6isqrt(2)
since both the 15i and 6i have the same sqrt value, you can combine them like this
(15i + 6i)sqrt(2)
since both the 15 and 6 are being multiplied by "i", you can combine them like this
21i * sqrt(2)
It should be written like this
21isqrt(2)

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2.)
(-4 + sqrt(-20))/2
(-4 + sqrt(-4 * 5))/2
(-4 + 2isqrt(5))/2
(-4/2) + ((2i)/2)sqrt(5)
-2 + isqrt(5)

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3.)
(7sqrt(-2))*(-4sqrt(-3))
(7 * -4) * sqrt(-2 * -3)
-28sqrt(6)

Try it own your calculator and see if you don't get the same value. Some calulators don't do "i", but you can go to www.quickmath.com to check. That site will calculate "i".

If you have any questions, just let me know.