i try to plot this equation        2.96736996560705*10^(-12)*p^2+1.31319840299485*10^(-13)*t^2-8.89549693662593*10^(-7)*p+8.53128393394231*10^(-7)*t-3.65558815509970*10^(-30)*p*t-1 = 0 and use this command plots:-implicitplot(TWeq, p = -10^10 .. 10^11, t = -3*10^8 .. 3*10^8, gridrefine = 3, scaling = constrained, size = [1000, 100]) but  it only shows like this

it should be an ellipse but it just show like this..please help me.

Hi,

I want to plot the Tsai Wu failure envelope for a given
composite. The Tsai Wu failure criterion (for a pure biaxial
state of stress) is given by:

F1*x+F2*y+F11*x^2+F22*y^2+F12*x*y=1

can someone help me?please.