Question

if a^2 + b^2 + c^2+ = 20 and a+b+c+ = 0. find ab+bc+ca

Answer 1

hey dear

refer to given attachment please

Answer 2

Given : - 
a² + b² + c² = 20
& a + b + c = 0

Now,
∵ ( a + b + c )² = a² + b² + c² + 2(ab + bc + ac)
∴ (0)² = 20 + 2(ab + bc + ac)
∴ 0 = 20 + 2(ab + bc+ ac)
∴ -20 = 2(ab + bc+ ac)
∴ ab + bc + ac = -20/2
∴ ab + bc + ac = -10.

Hope this helps you !
# Dhruvsh