var example_eqn = new Array('2(x+1)+x(x+1)+2x^2',
		'12x + 3 + x + -1 - 5x',
		'12x^2y^3 + 5x^2y^2 + 7x^2y^2 - 3x^2y^3',
		'2 * 3 + 2 * 6x + 4');
	
	var i = Math.floor(Math.random() * example_eqn.length);
	
	function example(){
		var form = document.getElementById('calcForm')
		form.expression.value = example_eqn[i];
		i += 1;
		if (i >= example_eqn.length)
			i = 0;
	}