f(x,y)=sqrt[4+2x^2-3y^2] at the point (2,1,3)

I found the tangent plane to be z=4/3(x-2)+1(y-1) which is correct but I can't get the linear approximation right at f(1.9,1.2). I keep getting 3.0666 and in my calculation I used 3+4/3(x-2)+1(y-1) and then plugged in 1.9 and 1.2 to get my answer, which is not correct according to the answers. Can someone help me out?