NSolve[x^7 - 4*x^3 == 1, x]

NSolve[x^7 - 4*x^3 == Sin[x], x]

FindRoot[x^7 - 4*x^3 == Sin[x], {x, -10}]

matice := {{1, 2, 3}, {2, 3, 5}, {3, 5, 7}}
vektor := {5, 7, 11}
LinearSolve[matice, vektor]

matice := {{1*a, 2, 3}, {2, 3, 5}, {3, 5, 
          7}}
vektor := {5, 7*sinalfa, 11}
LinearSolve[matice, vektor]

MainSolve[{x + a - 6*z == 5, x + y - a == 8, 
        z + 3*x == a}, {x, y, a}, z]

?DSolve

?Derivative

eqn := 
      L*i'[t] + r*i[t] == 
        U0*Sin[ω*t]
DSolve[eqn, i[t], t]

DSolve[{eqn, i[0] == i0}, i[t], t]

rovnice := y'[x] + y[x] == 
          Exp[-x];
podminka := y[0] == 0;
oborreseni = {x, 0, 5};

reseni = NDSolve[{rovnice, podminka}, y[x], oborreseni][[1]]; 
    Plot[Evaluate[y[x] /. reseni], Evaluate[oborreseni]]

Evaluate[y[x] /. reseni]

rovnice:=D[y'[x] + y[x], x] == Exp[-x];

rovnice