Question

If

a^2+b^2 +c^2= 1

then the range of ab + bc + ca is​

Answer 1

Civil Servant formerly belonged to IAS. a suared + b squared + c squared +2(ab+bc+ca) is always positive or zero being a square. And a squared + b squared + c squared is given as 1. Therefore range of ab+bc+ca is -1/2 to +infinity or (-1/2 +infinity) both -1/2 and infinity included.