We like to help you learn to do such tasks yourself, which requires that you show us where you need help:
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If you have no idea even how to start, I would begin by dividing both sides by [MATH]4\pi[/MATH], to isolate the square root; then square both sides. The next step can be a little tricky if you haven't done it recently, so I'd like to see your attempt so I can know what advice to offer.