Question

if a+b+c=10 and a2 +b2+ c2=38, then the value of [ab+bc+ca] is

Answer 1

Answer:

Step-by-step explanation:

a + b + c = 10. ⇒ (a + b + c)2 = (10)2. ⇒ a2 + b2 + c2 + 2ab + 2bc + 2ca = 100. ⇒ 38 + 2(ab + bc + ca) = 100. ⇒ 2(ab + bc + ca) = 62. ⇒ 2(ab + bc + ca)