Question

a+b+c = 40 , a² + b² + c² = 10 , then find value of ab + bc + ca​

Answer 1

We know,(a+b+c)²=a²+b²+c²+2ab+2bc+2ca

Now,

40²=10+2ab+2bc+2ca

1600-10=2ab+2bc+2ca

1590=2(ab+bc+ca)

1590/2=ab+bc+ca

795=ab+bc+ca

Answer 2

Answer:

795

Step-by-step explanation:

we know that

${(a + b + c)}^{2} = {a}^{2} + {b}^{2} + {c}^{2} + 2(ab + bc + ca)$

and

a+b+c = 40,

a² + b² + c² = 10

then

${40}^{2} = 10 + 2(ab + bc + ca)$

by solving this equation

ab + bc + ca = 795