If you use the pythagorean theorem formula...

(-4,5) = sqrt 41
I don't understand how they got sqrt 41.

h^2 = (-4)^2+5^2 = 16+25 = 41
h = sqrt(41)

Are you asking to find the distance from the origin to the point (-4,5) using the Pythagorean Theorem, and if the answer is 41?

a^2+b^2 = c^2
(5)^2+(4)^2 = c^2
25+16 = c^2
41 = c^2
√41 = √c^2
√41 = c

a^2+b^2=c^2

a=-4
b=5

So a^2 is 16 and b^2 is 25. Add them together to get 41. That's c^2. So you take the square root to get c, which is the length of the hypotenuse. Since there's no even square of 41, the final answer is sqrt(41).

4^2 + 5^2 = c^2

16 + 25 = c^2

41 = c^2

I hope this information was very helpful.

(-4)^2 + (5)^2 = c^2
16 + 25 = c^2
41 = c^2
sqrt(41) = sqrt(c^2)
c = sqrt(41)

(-4)^2+5^2=c^2
16+25=c^2
41=c^2
c=sqrt41