To be able to factor x + 4 from the last two terms, you need the unit coefficient to be 4 x 18 = 72, so you need to add and subtract 68: <span>(x + 4)x + 18x + 4 + 68 - 68 </span> <span>(x + 4)x + 18x + 72 - 68 </span> <span>(x + 4)x + (x + 4)18 - 68 </span>
<span>So you end up with: </span> <span>(x + 4)(x + 18) - 68 </span>
<span>Answer: </span> <span>Add and subtract 68</span>