Question

find the value of ab+bc+ca , if a+b+c+=9 and a + b+ c2 =35
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Answer 1

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Answer 2

Given a + b + c = 9 ----- (1)

Given a^2 + b^2 + c^2 = 35 ----- (2)

On squaring (1) on both sides, we get

= > (a + b + c)^2 = (9)^2

= > a^2 + b^2 + c^2 + 2ab + 2bc + 2ca = 81

= > a^2 + b^2 + c^2 + 2(ab + bc + ca) = 81

= > 35 + 2(ab + bc + ca) = 81

= > 2(ab + bc + ca) = 81 - 35

= > 2(ab + bc + ca) = 46

= > ab + bc + ca = (46)/2

= > ab + bc + ca = 23.

Hope this helps!