Algebra: Please help
posted by Jack on .
Solve for B: square root b^4/25 = 4.
A.) 2
B.) +/ 5 square root 2
C.) 3
D.) +/ 2 square root 5
I don't know how to do these so please show your work.
Thank you.

we cross multiply or multiply both sides by 25 to get b^4 = 100
sqrt of both sides gives us sqrt b^4 = sqrt 100 =
sqrt b^2 * b^2 = 10
b^2 = 10
b = +/ sqrt 10
which is roughly equal to +/ 3.1623... 
√(b^4/25) = 4
b^2/5 = 4
b^2 = 20
b = ±√20, but since 20=4*5,
b = ±2√5 
So which is it?

woops Steve is right, I did not see the sqrt before the equation.
So we get 16 = b^4/25
Simplifying we get 25*16 = 400
b^4 = 400
b^2 = 20
so, b^2 = sqrt 2^2 * 5
so, b = +/ 2 sqrt 5
answer is D
Sorry for inconvenience 
*Sorry for any inconveniences caused to you.

Thank you for all your help...I appreciate it.