If you were to solve this 64y^2 - 9 would it be y=.375?
What would this look like factored?
If you set it equal to zero, you have the difference of two squares equal to zero.
Can you think of something that, when squared, equals 64y^2 ?
Call that "a". Then "b" = 3.
a^2 - b^2 = (a + b)( a - b)
Setting this to zero and solving will give you two solutions.