Frequency describes the number of waves that pass a fixed place in a given amount of time.
Answer: We should add the constant 81 to the expression to have a perfect square trinomial.
The perfect square trinomial that would be formed would result from (x + 9)^2.
We can use foil to prove it.
(x + 9)(x + 9)
x^2 + 9x + 9x + 81
x^2 + 18x + 81
81 is the value that must go with 18x in the middle to form the perfect square trinomial.
9+3=12
30+20=50
300+100=400
Then add.
12+50+400=462
<span>So 339+123=462</span>
3x + 5 + 4x =180
7x + 5 = 180
7x = 175
x = 25
3(25) + 5
75 + 5
80
KL = 80