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If a+b+c=14, a2+b2+c2=74 and a3+b3+c3=434 find …

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If a+b+c=14, a2+b2+c2=74 and a3+b3+c3=434 find abc

  • 2 answers

Manish Gandhi 8 years, 4 months ago

We know, (a + b + c)2 = a2 + b+ c2 + 2(ab + bc + ca)     =>     (14)2 = 74 + 2(ab + bc + ca)     =>     ab + bc + ca = 122 / 2 = 61

Again, using a3 + b3 + c3 - 3abc = (a + b + c) (a2 + b+ c2 - ab - bc - ca)

434 - 3abc = 14 (74 - 61)

434 - 3abc = 14 (13)

434 - 3abc = 182

3abc =  434 - 182 = 252

Abc = 252/3 = 84 (Answer)

 

Rashmi Bajpayee 8 years, 7 months ago

(a + b + c)2 = a2 + b2 + c2 + 2(ab + bc + ca)     =>     (14)2 = 74 + 2(ab + bc + ca)     =>     ab + bc + ca = 122 / 2 = 61

Again, using a3 + b3 + c3 - 3abc = (a + b + c) (a2 + b2 + c2 + ab + bc + ca)

=>     434 - 3abc = 14 (74 - 61)

=>     -3abc = -252

=>     abc = 84

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