Question

If a-b-c=3 and a2+b2+c2=77 to find ab-bc+CA

Answer 1

$\huge \mathscr{\orange {\underline{\pink{\underline {Answer:-}}}}}$

a - b - c = 3

a² + b² + c² = 77

( a + (-b) + (-c)² = a²+b²+c²-2ab+2bc-2ca

9 = 77-2(ab-bc+ca)-(ab-bc+ca) = -34

=> ( ab - bc + ca ) = 34