Question

( t - 1 )² + ( t + 2 )² - 9 = 0

Answer 1

$(t-1)^2+(t+2)^2-9=0\\ (t^2-2t+1)+(t^2+4t+4)-9=0\\ 2t^2+2t-4=0\\ 2(t^2+t-2)=0\\ t^2+t-2=0~\Rightarrow~\Delta=9\\t=-2~\vee~t=1$