Question

If a+b+c=10 and a^2+b^2+c^2=42 find the value of ab+bc+ca

Answer 1

✍︎...... ☃︎ Aɴsᴡᴇʀ ☃︎

Given,

a2+b2+c2=60 and ab+bc+ca=42

We know,

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

Thus,

    (a+b+c)2=(a2+b2+c2)+2(ab+bc+ca)

=>(a+b+c)2=60+2(42)

=>(a+b+c)2=60+84

=>(a+b+c)=144

=>(a+b+c)=12

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