Question

hello frnds.....
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plzz help...
iwill mark u as brainliest...

Answer 1

Hi friend!
Here is your Answer!
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$(a + b + c) {}^{2} = {a}^{2} + {b}^{2} + {c}^{2} + 2(ab + bc + ca) \\ \\ now \: putting \: the \: value \\ \\ {5}^{2} = {a}^{2} + {b}^{2} + {c}^{2} + 2 \times 10 \\ \\ {a {}^{2} + {b}^{} }^{2} + {c}^{2} = 25 - 20 = 5 \\ \\ now \\ {a}^{2} + {b}^{2} + c {}^{2} - 3abc = \\ (a + b + c)(a {}^{2} + {b}^{2} + {c}^{2} - (ab + bc + ca) \\ \\ {a}^{2} + {b}^{2} + {c}^{2} - 3abc = (5) \times (5 - 10) \\ \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: = 5 \times - 5 = - 25 \\ hence \: proved$