Find each product. (7x+4y)(7x-4y)

Question

Accepted Answer

Welcome back. I'm so glad you're here. We've got to find the product of or multiply these two by no meals. We've got a four M. Plus eight N. Times four M minus eight N. And hey, I mean normally we just start foiling that out. But look how similar those are four M. Four M. Eight and eight. And that is this form A plus B A minus B. Which means we are dealing with something that is a difference of squares. If we were to go through and foil that whole thing out, we come out with a squared minus B squared and we can just go ahead and go straight to this. So for M. That's our A term squaring both of the 4, 16 the M. Squared and then minus B squared that's eight. And so 64 8 times 8, 64 squared. And that's our final answer. And if you'd like we can stick around and foil that out real quick. Otherwise you're good to go if that's all you need. But so if we go four M. Times four M. That's 16 M. Squared. We go four M. Times negative eight N. Is going to be negative 32 M. N. And we take the insides eight N. Times four M. Is going to be plus 32 M. N. Sorry, didn't change the color there. And then if we've got the lasts we've got eight end times negative eight and is going to be minus 64 squared. And yeah those two middle terms they're going to cancel right out. And that brings us straight back to 16 M squared minus 64 N. Squared. And as we said, answer choice A that's it you've got it will catch on the next one.

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