Question

If a + b – c = 4 and a2 + b2 + c2 = 38, find ab – bc – ca.

Answer 1

Answer:

As per the Question,

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

=> 10^2 = 38 + 2(ab+bc+ca)

=> ab + bc + ca = (100–38)/2= 31

MARK ME AS THE BRAINLIEST

Answer 2

Answer:

ab-bc-ca= -11

Step-by-step explanation:

here, a+b+(-c)=4

squaring both side,we get

= [a+b+(-c)]² = 4²

= a²+b²+c²+2(ab-bc-ca) = 16

= [a²+b²+c²]+2(ab-bc-ca) = 16

= 38+2(ab-bc-ca)=16

= 2(ab-bc-ca) = 16-38

= ab-bc-ca = -22/2

= ab-bc-ca = -11

so, ab-bc-ca = -11.