Distance Formula

How is the distance formula correctly written:

• $d\ =\ \sqrt{\left(y_{1\ }-\ y_2\right)^2\ -\left(x_{2\ }-\ x_1\right)^2}\$

• $d\ =\ \sqrt{\left(x_{2\ }-\ x_1\right)^2\ +\ \left(y_{2_{\ }}-\ y_1\ \right)^2}$

• $d\ =\ \sqrt{\left(y_{1\ }-\ y_2\right)^2\ +\ \left(x_{2\ }-\ x_1\right)^2}$

• d = $\sqrt{\left(x\right)^2-\ \left(y\right)^2}$

A(3,1) B(-2,-1) written correctly is:

• $\sqrt{\left(-2-3\right)^2\ +\ \left(-1-1\right)^2}$

• $\sqrt{\left(1-3\right)^2\ +\ \left(-1-2\right)^2}$

• $\sqrt{\left(-2-3\right)^2\ -\ \left(-1-1\right)^2}$

• $\sqrt{\left(-2-3\right)^2\ -\ \left(-1-1\right)^2}$

Find the distance.

• 9.7
• 10.7
• 11.7
• 12.7