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# powm1

> Evaluate `bˣ - 1`.

<section class="intro">

<!-- <equation class="equation" label="eq:exponential_function_minus_one" align="center" raw="y = b^x - 1" alt="Exponential function minus one"> -->

<div class="equation" align="center" data-raw-text="y = b^x - 1" data-equation="eq:exponential_function_minus_one">
    <img src="https://cdn.rawgit.com/stdlib-js/stdlib/7e0a95722efd9c771b129597380c63dc6715508b/lib/node_modules/@stdlib/math/base/special/powm1/docs/img/equation_exponential_function_minus_one.svg" alt="Exponential function minus one">
    <br>
</div>

<!-- </equation> -->

When `b` is close to `1` and/or `x` is small, this implementation is more accurate than naively computing `bˣ` minus `1`.

</section>

<!-- /.intro -->

<section class="usage">

## Usage

```javascript
var powm1 = require( '@stdlib/math/base/special/powm1' );
```

#### powm1( b, x )

Evaluates `bˣ - 1`.

```javascript
var y = powm1( 2.0, 3.0 );
// returns 7.0

y = powm1( 4.0, 0.5 );
// returns 1.0

y = powm1( 0.0, 100.0 );
// returns -1.0

y = powm1( 100.0, 0.0 );
// returns 0.0

y = powm1( 0.0, 0.0 );
// returns 0.0

y = powm1( 3.141592653589793, 5.0 );
// returns ~305.0197

y = powm1( NaN, 3.0 );
// returns NaN

y = powm1( 5.0, NaN );
// returns NaN
```

</section>

<!-- /.usage -->

<section class="examples">

## Examples

<!-- eslint no-undef: "error" -->

```javascript
var randu = require( '@stdlib/random/base/randu' );
var round = require( '@stdlib/math/base/special/round' );
var powm1 = require( '@stdlib/math/base/special/powm1' );

var b;
var x;
var y;
var i;

for ( i = 0; i < 100; i++ ) {
    b = round( randu()*10.0 );
    x = round( randu()*10.0 ) - 5.0;
    y = powm1( b, x );
    console.log( '%d^%d - 1 = %d', b, x, y );
}
```

</section>

<!-- /.examples -->

<section class="links">

</section>

<!-- /.links -->
