<p>Our AP Cal Teacher gave us this problem to solve, even though it doesn't have anything to do with Calc!!!!
Help would be appreciated....
Find a^2 + B^2 + c^2 if:
a+b+c=13 and ab + bc+ ac=47</p>
<p>Take the square of a+b+c=13 to get a^2 + b^2 + c^2 + 2ab + 2bc + 2ac = 169</p>
<p>Substitute in 47*2 for 2ab+2bc+2ac to get a^2 + b^2 +c^2 = 75</p>
<p>Voila.</p>
<p>thanks- I got that too.</p>
<p>BTW that's a standard AMC 12 question.</p>