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If a+b-c=5 and a²+b²+c²=29 find the value of ab-bc-ca

Answer»

Answer:

Step-by-step EXPLANATION:

Given that,

a+b-c = 5 and a^2+b^2+c^2 = 29

Using the formula

(a+b+c)^2 = a^2+b^2+c^2+2(ab+bc+ca)

=>(a+b+(-c)^2= a^2+b^2+c^2+2(ab+bc+ca)

=>(a+b-c)^2= a^2+b^2+c^2+2(ab-bc-ca)

=>5^2= 29+2(ab-bc-ca)

=>25= 29+2(ab-bc-ca)

=>ab-bc-ca= 25-29/2

=>ab-bc-ca= -4/2

=>ab-bc-ca= -2

Ans: -2

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