Question 131

If $$a + b +c= 6$$, $$a^{2}+ b^{2}+ c^{2} = 14$$, find the value of $$bc + ca + ab$$.

Solution

It is given that : $$a + b + c = 6$$ and $$a^{2}+ b^{2}+ c^{2} = 14$$

Also, $$(a + b + c)^2 = a^2 + b^2 + c^2 + 2(ab + bc + ca)$$

=> $$6^2 = 14 + 2(ab + bc + ca)$$

=> $$ab + bc + ca = 22/2 = 11$$

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