Question

If a-b=3 b-c=5 then value of a²+b²+c²-ab-bc-ca is?

Answer 1

a-b=3⇒a=3+b ....(i) and b=a-3
b-c=5⇒c=b-5.....(ii)⇒a-3-c=5⇒c-a=-8
a²+b²+c²-ab-bc-ca
a²-ab+b²-bc+c²-ca
a(a-b)+b(b-c)+c(c-a)
3a+5b-8c
3a+5 (a-3)-8(-8+a)
3a+5a-15+64-8a
8a-8a+49
=49
Value is 49.