A irrational number is a number that can't be expressed as a ratio of two whole numbers. That's it.
For examples (in increasing order of difficulty)
1 is a rational number because it is 1/1
0.75 is a rational number because it is equal to 3/4
2.333... (infinite number of digits, all equal to three) is rational because it is equal to 7/3.
sqrt(2) is not a rational number. This is not completely trivial to show but there are some relatively simple proofs of this fact. It's been known since the greek.
pi is irrational. This is much more complicated and is a result from 19th century.
As you see, there is absolutely no mention of the digits in the definition or in the proofs I presented.
Now the result that you probably hear about and wanted to remember (slightly incorrectly) is that a number is rational if and only if its decimal expansion is eventually periodic. What does it mean ?
Take, 5/700 and write it in decimal expansion. It is 0.0057142857142857.. As you can see the pattern "571428" is repeating in the the digits. That's what it means to have an eventually periodic decimal expansion. The length of the pattern can be anything, but as long as there is a repeating pattern, the number is rational and vice versa.
As a consequence, sqrt(2) does not have a periodic decimal expansion. So it has an infinite number of digits but moreover, the digits do not form any easy repeating pattern.
Answer:
5-(1+5)= -1
-2(1+4)=-10
Step-by-step explanation:
Answer:
Prime.
Step-by-step explanation:
First let's multiply our outer coefficients in this case 1 and 8, so we have 1x8=8. Now the point of this is to get the factors of 8 and see if we can get that middle term -7. Factors of 8 are 1x8, 2x4 and that's it. From there I notice that -8+1 = -7 and so:
Notice that the (x-8) and (x+8) are not the same factors, therefore the factors are not any of those answer choices and so it's prime. You can calculate the factors by using the quadratic formula, however I think that is beyond the scope of this question.
Given Mr. Engle’s total income, I = $52,000 and total expenses, E = $53,800, solving for average difference between income and expenses per month:
(I-E)/12 = ($52,000 - $53,800)/12
(I-E)/12 = - $1,800/12
(I-E)/12 = -$150
This means that Mr. Engle’s expenses exceed his income by an average of $150 each month in the said year.
We can always split a regular polygon with 
sides into triangles, whose base is the side of the polygon and whose height is the apothem of the polygon. So, the sum of the areas of all these triangles is
where is the number of sides, 
is the side length, and 
is the apothem length.
So, you just need to plug you values in: in your case, you have 
So, the formula becomes
