49x^2 - 9 = 0
As there is no x term, we can pretty much guess we have a situation where we factlrise by something known aa difference of two squares, so to factorise it:
49 = 7^2
9 = 3^2
x^2 = (x)^2
so...
(7x - 3)(7x + 3) = 0
7x - 3 = 0 7x + 3 = 0
x = 3/7 x = -3/7
V = 2ab + 2ca + 2bc
2ab + 2ca = V - 2bc
2a * b + c = V - 2bc
Answer: a = v - 2bc / 2 * b + c
Hope that helps!!!!! : )