Question

If a+b+c=10and a^2+b^2+c^2=40find ab+bc+ac.

Plz....Plz.... Please answer it....Plz...

Answer 1

Hey !!!

a + b + c = 10 --[given ]
a² + b² + c² = 40

we know a formula .

(a + b + c )² = a² + b² + c² + 2ab + 2bc + 2ca

(a + b + c )² - (a² + b² + c² ) = 2 (ab + bc + ca )

10² - 40 = 2 (ab + bc + ca )

100 - 40 = 2 (ab + bc + ca )

60 /2 = ab + bc + ca

30 = ab + bc + ca

hence, ab + bc + ca = 30 Ans

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Hope it helps you !!!

@Rajukumar111

Answer 2

a+b+c=10
a^2+b^2+c^2=40
ab+bc+ac=?
(a+b+c)^2=a^2+b^2+c^2+2(ab+bc+ac)
(10)^2=40+2(ab+bc+ac)
100=40+2(ab+bc+ac)
100-40=2(ab+bc+ac)
60=2(ab+bc+ac)
60/2=ab+bc+ac
30=ab+bc+ac