Express your answer using two significant figures.
Work = change in electric potential. The formula for electric potential is given by V = (k * q1 * q2) / r. Note that the work will be negative since like charges repel:
W = (k * q1 * q2) / r
W = 8.9875 * 109 * -0.0000015 * -0.0000015 / 0.009
W = 2.246875 J
Round to 2 significant figures and make negative since the charges are repelling each other:
W = -2.2 J
Note: Mastering Physics took -2.3 J as the answer for me. It’s a rounding type issue because Mastering Physics sometimes uses a Coulomb Constant of 9 * 109 instead of the more correct 8.9875 * 109