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If a²+b²+c²=80 and a+b+c=20, then fimd the value of ab+bc+ca. |
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Answer» Square on both sides, ( a + b + c )^2 = 20^2 => a^2 + b^2 + c^2 +2( ab + bc + CA ) = 400 putting the given VALUES, => 80 + 2( ab + bc + ca ) == 400 => 2( ab + bc + ca ) = 320 => ab + bc + ca = 320/2 => ab + bc + ca = 160 |
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