Question

If a + b + c = 13, a^2 +
b^2 + c^2 = 69, then (ab +
bc + ca) = ?
Select one:
O
O a. 1
O b. 50
O c. 51
O d. 52
O e. 53​

Answer 1

Answer:

50 is your ans

Step-by-step explanation:

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

2(ab+bc+ca)=(a+b+c)2-(a2+b2+c2)=169-69=100=(ab+bc+ca)=50

Answer 2

Use formula and substitute

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

(13)^2 = 69 + 2(ab+bc+ca)

169-69 = 2(ab+bc+ca)

100 = 2(ab+bc+ca)

ab+bc+ca = 100/2 = 50