function gaxpy( N, alpha, x, strideX, y, strideY ) {
	return ndarray( N, alpha, x, strideX, stride2offset( N, strideX ), y, strideY, stride2offset( N, strideY ) ); // eslint-disable-line max-len
}
Multiplies `x` by a constant and adds the result to `y`.

@param {PositiveInteger} N - number of indexed elements
@param {number} alpha - scalar
@param {NumericArray} x - input array
@param {integer} strideX - `x` stride length
@param {NumericArray} y - output array
@param {integer} strideY - `y` stride length
@returns {NumericArray} output array

@example
var x = [ 1.0, 2.0, 3.0, 4.0, 5.0 ];
var y = [ 1.0, 1.0, 1.0, 1.0, 1.0 ];
var alpha = 5.0;

gaxpy( x.length, alpha, x, 1, y, 1 );
// y => [ 6.0, 11.0, 16.0, 21.0, 26.0 ]