private void button1_Click(object sender, EventArgs e)
{
ingresar = new Resta();
ingresar.R1 = double.Parse(textBox1.Text);
ingresar.R2 = double.Parse(textBox2.Text);
label3.Text = ingresar.Calcular().ToString();
}
private void button1_Click(object sender, EventArgs e)
{
rest = new Resta();
rest.R11 = double.Parse(txtValA.Text);
rest.R21 = double.Parse(txtValB.Text);
lblResult.Text = Convert.ToString(rest.Calcular());
}