Question

Find the value of ab+bc+ ac when, a+b+c=10 and a2 +b2 +c2 =20

Answer 1

Answer:

40

Step-by-step explanation:

let ab+bc+ac = X

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

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

20 = 10² - 2X

2x = 100 - 20

2x = 80

x = 80÷2

X = 40

thus, ab+bc+ca = 40