Browse · MATH Print → jmc algebra intermediate Problem If the sum of the squares of nonnegative real numbers a,b, and c is 39, and ab+bc+ca=21, then what is the sum of a,b, and c? Solution — click to reveal Since (a+b+c)2=a2+b2+c2+2ab+2bc+2ca=(39)+2(21)=81, it follows that a+b+c=±9. Since a,b,c≥0 we find a+b+c=9. Final answer 9 ← Previous problem Next problem →