I used an online math site, to explain quadratic equations. But the thing is, they said that (-4)^2 is 16, but my calculator said -16. Why is that? And also, how does the square root of 40 break down into the square root of 4 and the square root of ten? Does this have to do with GCF's?

Question

I used an online math site, to explain quadratic equations.  But the thing is, they said that (-4)^2 is 16, but my calculator said -16.  Why is that? And also, how does the square root of 40 break down into the square root of 4 and the square root of ten? Does this have to do with GCF's?

drwls · Answer

Your calculator is wrong.
Enter 4, then press the "change of sign" button (if you have one) to get -4 in the display, and then hit x^2.

If you still get -16, get a better calculator , or call them for tech help. I hope you saved your receipt.

sqrt 40 = sqrt (4*10) = 2 sqrt 10

This has nothing to do with GCF's