The term "closed" in math means that if you take two items from a set, do some operation, then you'll always get another value in the same set (sometimes you may get the same value as used before). For example, adding two whole numbers leads to another whole number. We therefore say "the set of whole numbers is closed under addition". This applies to integers as well because integers are positive and negative whole numbers. So we can say that integers are closed under addition.
Integers are not closed under division. Take two integers like 2 an 5 and divide: 2/5 = 0.4 which is not an integer. Integers don't have decimal parts.
The set of whole numbers is {0,1,2,3,...} and we can subtract the two values 1 and 2 to get 1-2 = -1. The order matters here. Subtracting a larger value from a smaller leads to a negative. The value -1 is not in the set of whole numbers. So we can say that whole numbers is not closed under subtraction
Finally, the set of irrational numbers is closed under addition. Adding any two irrational numbers leads to another irrational number. For instance, pi+sqrt(2) = 3.142 + 1.414 = 4.556; I'm using rounded decimals as approximate values. An irrational number is one where we cannot write it as a fraction of integers. Contrast that with a rational number in which we can write it as a fraction of integers. Example: 10 = 10/1 is a rational number.
Answer:
x-intercept = 9 y-intercept = 5
Step-by-step explanation:
Answer: -2x+3y = 21 which is choice C
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Work Shown:
The slope of the original line is -3/2. The perpendicular slope is 2/3. We flip the fraction and flip the sign. Multiplying the original slope (-3/2) and the perpendicular slope (2/3) will result in -1. Let's use this perpendicular slope and the point to find the equation of the perpendicular line in slope intercept form.
y = m+b
y = (2/3)x+b .... plug in the perpendicular slope
9 = (2/3)(3)+b .... plug in the point (x,y) = (3,9)
9 = 2+b
9-2 = 2+b-2 ... subtract 2 from both sides
b = 7
So y = (2/3)x+b turns into y = (2/3)x+7.
This equation is in slope intercept form.
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Let's convert to standard form
y = (2/3)x+7
3*y = 3*((2/3)x+7) ... multiply both sides by 3 to clear out the fraction
3*y = 3*(2/3)x+3*7 ... distribute
3y = 2x+21
-2x+3y = 21 .... get the x term to the other side (subtract 2x from both sides)
C is true because the slope for johan is 15 compared to Rowans slope which is 5
