Una progresión aritmética o secuencia aritmética es una secuencia de números tal que la diferencia entre los términos consecutivos es constante. Por ejemplo, la secuencia 5, 7, 9, 11, 13, 15 ... es una progresión aritmética con una diferencia común de 2
Answer: x° = 20
Steps:
100 + x + 3x = 180
x + 3x = 80
4x = 80
x = 80/4
x = 20
Check:
100 + x + 3x = 180
100 + 20 + 3(20) = 180
100 + 20 + 60 = 180
180 = 180 ✅
Given:
The equations of parabolas in the options.
To find:
The steepest parabola.
Solution:
We know that, if a parabola is defined as

Then, the greater absolute value of n, the steeper the parabola.
It can be written as


where
, the smaller absolute value of p, the steeper the parabola.
Now, find the value of |p| for eac equation
For option A, 
For option B, 
For option C, 
For option D, 
Since, the equation is option A has smallest value of |p|, therefore, the equation
represents the steepest parabola.
Hence, the correct option is A.
If you expand the square, you have

Simplify the right hand side:

Cancel the -3x appearing on both sides:

Multiply both sides by 4:

Consider the square root of both terms (using the doubles sign):

Look at the table for the people that used Lithium.
There are 18 relapses, 6 No relapses with a total of 24 people.
The relative frequency for relapse, would be dividing the number of relapses by the total number of people.
This would be D. 18 / 24 = 75%