for least squares pm2 5 = 0+1humidity+2dewpoint+3se+4ne+5nw+6windspeed if You suspect that the relationship between humidity and PM2.5 concentration...

for least squares pm2 5 = β0+β1humidity+β2dewpoint+β3se+β4ne+β5nw+β6windspeed

if You suspect that the relationship between humidity and PM2.5 concentration may be a quadratic relationship.

what would the new equation be?

is it pm2 5 = β0+β1humidity+β2humidity^2+β3dewpoint+β4se+β5ne+β6nw+ β7windspeed