# Function lsolve Finds one solution of a linear equation system by forwards substitution. Matrix must be a lower triangular matrix. Throws an error if there's no solution. `L * x = b` ## Syntax ```js math.lsolve(L, b) ``` ### Parameters Parameter | Type | Description --------- | ---- | ----------- `L` | Matrix, Array | A N x N matrix or array (L) `b` | Matrix, Array | A column vector with the b values ### Returns Type | Description ---- | ----------- DenseMatrix | Array | A column vector with the linear system solution (x) ## Examples ```js const a = [[-2, 3], [2, 1]] const b = [11, 9] const x = lsolve(a, b) // [[-5.5], [20]] ``` ## See also [lsolveAll](lsolveAll.md), [lup](lup.md), [slu](slu.md), [usolve](usolve.md), [lusolve](lusolve.md)