Question

If xy+yz+zx=35 and x^2+y^2+z^2=155, find the value of 3(x+y+z)

Answer 1

Answer:

(a+b+c)²=a²+b²+c²+2(ab+bc+ac) [Algebraic Identity]

Using this identity,

x+y+z={(x²+y²+z²)+2(xy+yz+zx)}½

={155+2(35)}½

=(155+70)½

=√225

=15.(Ans)