tanα=3
sinα/cosα=3
sin^2α/cos^2α=9
(1-cos^2α)/cos^2α=9
1/cos^2α-1=9
cos^2α = 1/10
3sinα^2-sinαcosα+2
= cos^2α(3tan^2α-tanα)+2
= 1/10*(3*3^2-3) + 2
= 12/5+2
= 22/5