Question

if a+b-c=6 and a²+b²+c²=40 then find the value of ab-bc-ca​

Answer 1

Explanation:

$a+b-c=6$

$(a+b-c)^2=6^2$

$a^2 + b^2 + c^2 + 2(ab -bc - ca)=36$

$2(ab-bc-ca)+ 40 = 36$

$2(ab-bc-ca)=36-40=-4$

$ab-bc-ca=\frac{-4}{2}=-2$

Answer: -2

I hope this answer helps. :D