Solving equations like ax² + c = 0 can be quite straightforward.
From your work on algebra, you should be able to rearrange the equation to: x² = 25
By taking the square-root of both sides, we end up with:
That wasn't too bad, was it? Another solution is x = -5, but we'll look at that another time.
Here's one for you. Find the solution to the equation: x² - 121 = 0.