Question

Factorise ! 2 3 -28 1
If a2 + b2 + c2 = 80 and a + b + c = 20, then find the value of ab + bc + ca​

Answer 1

Answer:

160

Step-by-step explanation:

(a+b+c)²=a²+b²+c²+2(ab+bc+ca)

⇒20²=80+2(ab+bc+ca)

⇒400-80=2(ab+bc+ca)

⇒320/2=ab+bc+ca

⇒160=ab+bc+ca