If a + b + c = 11 and a2 + b2 + C2 = 81, find :
ab + bc + ca.
Answers
Answered by
3
Answer:
ab +bc +ca is 20 hence 20 is correct answer
Attachments:
Answered by
8
Given
a + b + c = 11
a^2 + b^2 + c^2 = 81
Find
ab + bc + ca
solution
=> (a + b +c)^2 = a^2 + b^2 + c^2 + 2 ( ab + bc + ca)
=> (11)^2 = 81 + 2 (ab + bc + ca)
=> 2 (ab + bc + ca) = 121 - 81
=> 2( ab + bc + ca) = 40
=> (ab + bc + ca) = 40 / 2
=> ab + bc + ca = 20
Similar questions