[Fact] public void Limit4() =>
Test(@"\lim_{xf\to 1+x} \left[\frac{1}{x}\right]", MathS.Limit("1/x", "xf", "1+x"));
[Fact] public void Limit5() =>
Test(@"\lim_{xf\to {x_{2}}^{3}} \left[{x}^{23}-x_{16}\right]", MathS.Limit("x^23-x_16", "xf", "x_2^3"));
[Fact] public void Limit3() =>
Test(@"\lim_{x\to \infty } \left[x+y\right]", MathS.Limit("x + y", x, Real.PositiveInfinity));