Question

If a+b+c=11 and ab+ bc+
ca=15 then a^2+ b^2+c^2 =​

Answer 1

Solution :

⇛a + b + c = 11

⇛ab + bc + ca = 15

⇛a² + b² + c² = ???

›(a+b+c)² = a² + b² + c² +2ab+2bc+2ca

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

›› a² + b² + c² = (11)² -2(15)

›› a² + b² + c² = 121 - 30

›› a² + b² + c² = 91

Hence

• value of a² + b² + c² = 91

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