Question

Q3
If a + b +c = 12 and a? + b + c = 64 then find the value of (ab+bc +ca).

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Answer 1

Answer:

ab+bc+ca = 40

Step-by-step explanation:

given :

a+b+c= 12 and a²+b²+c²=64

ab+bc+ca=?

(a+b+c+)²= a²+b²+c²+2(ab+bc+ca)

=> (12)²=64+2(ab+bc+ca)

=> 144= 64+2(ab+bc+ca)

=> 144-64=2(ab+bc+ca)

=>80=2(ab+bc+ca)

=> 80/2= ab+ bc+ca

=> ab+bc+ca= 40

Answer 2

Correct Question:

If a + b +c = 12 and a² + b² + c² = 64 then find the value of (ab + bc + ca).

Given:

• (a + b + c) = 12

• a² + b² + c² = 64

To find:

1. Value of (ab + bc + ca)

Method:

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

⇒ (12)² = (a² + b² + c²) + 2(ab + bc + ca)

⇒ 144 = 64 + 2(ab + bc + ca)

⇒ 144 - 64 = 2(ab + bc + ca)

⇒ 2(ab + bc + ca) = 80

⇒ (ab + bc + ca) = 80 ÷ 2

⇒ (ab + bc + ca) = 40