Question

solution for this problem​

Answer 1

Answer:

(a+b+c) ² = a²+b²+c²+2(ab+bc+ac)

=>2(ab+bc+ac) = (a+b+c)² - (a²+b²+c²)

=> 2(ab+bc+ac) = (9)² - (35)

ab+bc+ac = (81-35)/2

=> ab+bc+ac = 23

Answer 2

Step-by-step explanation:

Given -

a + b + c = 9

a² + b² + c² = 35

To Find -

Value of ab + bc + ca

Now,

As Given :-

a + b + c = 9

Squaring both sides :-

» (a + b + c)² = (9)²

» a² + b² + c² + 2ab + 2bc + 2ca = 81

As Given :-

• a² + b² + c² = 35

» 35 + 2ab + 2bc + 2ca = 81

» 2ab + 2bc + 2ca = 81 - 35

» 2(ab + bc + ca) = 46

» ab + bc + ca = 46/2

• » ab + bc + ca = 23

Hence,

The value of ab + bc + ca is 23.

Formula Used :-

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

Some related formulas :-

• (a + b)² = a² + 2ab + b²
• (a - b)² = a² - 2ab + b²
• (a + b)(a - b) = a² - b²
• (a + b)³ = a³ + 3a²b + 3b²a + b³
• (a - b)³ = a³ - 3a²b + 3b²a - b³