# Function usolve #

Finds one solution of a linear equation system by backward substitution. Matrix must be an upper triangular matrix. Throws an error if there’s no solution.

`U * x = b`

## Syntax #

```
math.usolve(U, b)
```

### Parameters #

Parameter | Type | Description |
---|---|---|

`U` |
Matrix, Array | A N x N matrix or array (U) |

`b` |
Matrix, Array | A column vector with the b values |

### Returns #

Type | Description |
---|---|

DenseMatrix | Array | A column vector with the linear system solution (x) |

### Throws #

Type | Description —- | ———–

## Examples #

```
const a = [[-2, 3], [2, 1]]
const b = [11, 9]
const x = usolve(a, b) // [[8], [9]]
```