if a^2+b^2+c^2=90,a+b+c=20 then find the vale of ab+bc+ca.
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Answer:
Given :-
- a² + b² + c² = 90
- a + b + c = 20
Find Out :-
- ab + bc + ca
Solution :-
we know,
➪ (a + b + c)² = a² + b² + c² + 2ab + 2bc + 2ca
➭ (a + b + c)² = a² + b² + c² + 2(ab + bc + ca)
➭ (20)² = 90 + 2(ab + bc + ca)
➭ 400 = 90 + 2(ab + bc + ca)
➭ 400 - 90 = 2(ab + bc + ca)
➭ 310 = 2(ab + bc + ca)
➭ ab + bc + ca = 310/2
➭ ab + bc + ca = 155
∴ The value of ab + bc + ca is 155
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