Question

if a + b + C is equal to 18 and a square + b square + C is equal to 70 then value of a b + BC + CA​

Answer 1

✍ Given :-

• ( a + b + c) = 18

• a² + b² + c² = 70

✍ To Find :-

• ab + bc + ca

✍ Solution :-

We know that,

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

By putting the above values in the above identity, we get ,

➠ ( 18) ² = 70 + 2( ab + bc + ca)

➠ 324 - 70 = 2(ab + bc + ca)

➠ 254 = 2(ab + bc + ca)

➠ ( ab + bc + ca) = 254/2 = 127

More Formulas :-

• (a + b) ² = a² + b² + 2ab

• ( a - b) = a² + b² - 2ab

• ( a + b) ³ = a³ + b³ + 3ab ( a + b)

• (a - b) ³ = a³ - b³ - 3ab ( a - b)