k + 18k + 81 = 19k + 81 which cannot be factorised.
HOWEVER
If the question was about k2 + 18k + 81, but was foiled by the inability of this browser, then the answer is
k2 + 18k + 81 = (k + 9)2
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30=18k
Na+-K+ ATPase
K+15
0
Oh, dude, 2k plus k is like adding two of your favorite snacks plus one more - it's just 3k. So, if k represents a candy bar, then 2k plus k equals 3 candy bars. Easy peasy, right?