Question

If a+b+c=9 and a²+b²+c²=41,find ab+bc+ca

Answer 1

Answer:

Your answer

Step-by-step explanation:

a+b+c= 9

a^2 + b^2 + c^2 = 41

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

(9)^2 = 41 + 2( ab + bc + ca )

81 = 41+ 2( ab + bc + ca )

81-41 = 2( ab + bc + ca )

40 = 2( ab + bc + ca )

ab + bc + ca = 40/2

ab + bc + ca = 20