Question

if a^2 +b^2+c^2=90and a+b+c=20 then find ab+BC+ca​

Answer 1

Answer:

Please mark my answer as Brainliest.

Step-by-step explanation:

(a + b + c)2 = a2 + b2 + c2 + 2ab + 2bc + 2ca

(a+ b + c)2 = a2 + b2 + c2+ 2 (ab + bc + ca)

(20)2 = 90 + 2 (ab + bc + ca)

400 - 90 = 2 (ab + bc + ca)

ab + bc + ca = 155

Answer 2

your answer is 155 you can do by a+b+c whole square formula