Question

if a+b+c=20and a²+b²+c²=90 find the value of ab+bc+ac​

Answer 1

Hey mate !!

here's your answer....

»on basis as formula :

-›(a+b+c)²=[a²+b²+c²+2ab+2bc+2ca]

so here,

-›(20)²=[{a²+b²+c²}+2(ab+bc+ca)]

-›(20)²=[{90}+2(ab+bc+ca)]

-›400=90{2(ab+bc+ca)}

-›2(ab+bc+ca)=400-90

-›(ab+bc+ca)=310/2

-›(ab+bc+ca)=155 Answer.....

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