Matrix Null Space (Kernel) and Nullity Calculator

Find the null space of $$$\left[\begin{array}{ccc}1 & -1 & -1\\2 & -2 & 1\end{array}\right]$$$.

The reduced row echelon form of the matrix is $$$\left[\begin{array}{ccc}1 & -1 & 0\\0 & 0 & 1\end{array}\right]$$$ (for steps, see rref calculator).

To find the null space, solve the matrix equation $$$\left[\begin{array}{ccc}1 & -1 & 0\\0 & 0 & 1\end{array}\right] \left[\begin{array}{c}x_{1}\\x_{2}\\x_{3}\end{array}\right] = \left[\begin{array}{c}0\\0\end{array}\right].$$$

If we take $$$x_{2} = t$$$, then $$$x_{1} = t$$$, $$$x_{3} = 0$$$.

Thus, $$$\mathbf{\vec{x}} = \left[\begin{array}{c}t\\t\\0\end{array}\right] = \left[\begin{array}{c}1\\1\\0\end{array}\right] t.$$$

This is the null space.

The nullity of a matrix is the dimension of the basis for the null space.

Thus, the nullity of the matrix is $$$1$$$.

The basis for the null space is $$$\left\{\left[\begin{array}{c}1\\1\\0\end{array}\right]\right\}$$$A.

The nullity of the matrix is $$$1$$$A.