a + b + c = 1 , a 2 + b 2 + c 2 = 9 , a 3 + b 3 + c 3 = 1 , then find a 1 + b 1 + c 1
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a 1 + b 1 + c 1
⇒ a b c a b + b c + c a ---->(1)
We know that
( a + b + c ) 2 = a 2 + b 2 + c 2 +2(ab+bc+ca)
By substituting the given values in the above identity, we get
2(ab+bc+ca)=1-9
⇒ ab+bc+ca=-4---->(2)
We know that
a 3 + b 3 + c 3 =(a+b+c)( a 2 + b 2 + c 2 -(ab+bc+ca))+3abc
By substituting the given values and (1) in the above identity, we get
1=(1)(9-(-4))+3abc
⇒ 3abc=-12
⇒ abc=-4---->(3)
(1)= ( 3 ) ( 2 )
⇒ ( − 4 ) ( − 4 ) = 1
(a+b+c)^2=a^2+b^2+c^2+2ab+2bc+2ca So value of ab+bc+ca is -4
And from a^3+b^3+c^3=(a+b+c+)(a^2+b^2+c^3) + 3abc And value of abc come -4 1/a+1/b+1/c= (ab+bc+ca)/abc =-4/-4 U gotta answer and I gotta nothing :-( Nice question Sarthak ghoda gadi.......:-P
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a 2 + b 2 + c 2 = ( a + b + c ) 2 − 2 ( a b + b c + c a ) = 9
p u t t i n g v a l u e s i n t h i s ,
1 − 2 ( a b + b c + c a ) = 9
a b + b c + c a = − 4 − − − − − − − − − − − − ( 1 )
n o w
( a 2 + b 2 + c 2 ) ( a + b + c ) = a 3 + b 3 + c 3 + a b ( a + b ) + b c ( b + c ) +
c a ( c + a ) = 9
1 + a b ( 1 − c ) + b c ( 1 − a ) + c a ( 1 − b ) = 9
a b + b c + c a − 3 a b c = 8
a b c = − 4 − − − − − − − − − − − − − − − − ( 2 )
m o d i f y i n g t h e e x p r e s s i o n w e n e e d t o f i n d ,
a 1 + b 1 + c 1 = a b c a b + b c + c a
p u t t i n g ( 1 ) a n d ( 2 ) , w e g e t
− 4 − 4 = 1