if a²+b²+c²=80 and a+b+c=20, then fimd the value of ab+bc+ca.
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Answered by
3
a + b + c = 20
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
Answered by
2
a + b + c = 20
squaring both sides
( a + b + c )² = (20)²
a²+b²+c²+2(ab+bc+ca) = 400
80 + 2(ab + bc + ca) = 400
2(ab+bc+ca) = 320
ab + bc + ca = 160
squaring both sides
( a + b + c )² = (20)²
a²+b²+c²+2(ab+bc+ca) = 400
80 + 2(ab + bc + ca) = 400
2(ab+bc+ca) = 320
ab + bc + ca = 160
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