One of the tools that's great to keep in your algebra toolbox for the rest of your life is:

The product of (sum of 2 things) (difference of 2 things) = (difference in their squares).

For example: (x + y) (x - y) = (x² - y²)

When you're trying to factor algebra expressions, it's always good to keep your eyes open for the difference of two squares, and remember that it's going to be (sum) x (difference) of the things that they're squares of.

Here you have (a sum) x (a difference) of the same 2 things:

<span><u>(5a + 2bc) (5a - 2bc)</u></span>

You can multiply them out, or just use the little tool above:

(5a)² = 25a²

(2bc)² = 4b²c²

So (their sum) x (their difference) is <u>(25a² - 4b²c²)</u> .