function temmeRootFinder( t, a ) {
	return roots;

	/**
	* Calculates roots.
	*
	* @private
	* @param {number} x - function value
	* @returns {Array} function roots
	*/
	function roots( x ) {
		var f1;
		var f;
		var y;

		y = 1.0 - x;
		if ( y === 0.0 ) {
			return [ -BIG, -BIG ];
		}
		if ( x === 0.0 ) {
			return [ -BIG, -BIG ];
		}
		f = ln( x ) + ( a * ln( y ) ) + t;
		f1 = ( 1.0 / x ) - ( a / y );
		return [ f, f1 ];
	}
}
Helper function used by root finding code to convert `eta` to `x`.

@private
@param {number} t - first parameter
@param {number} a - second parameter
@returns {Function} root function