Answer:
C and D
Step-by-step explanation:
The quadratic formula is
x= (-b±√b²-4ac)/2a
The formula uses the numerical coefficients in the quadratic equation.
The general quadratic equation is ax²+bx+c where a, b and c are the numerical coefficients
So, lets try and see;
A.

But due to the fact that in this equation you have x⁴, the equation is not a quadratic equation thus can not be solved using this formula
B

C

D.

From the checking above, the equations will be C and D
Answer:
Equations:
--- Cindy
--- Ruben
Solution to equation:
Time they have the same amount: 14 minutes
Number of cards they have at that time: 140 flashcards
Step-by-step explanation:
Solving (a): Variables and what they represent
The variables to use are x and y
Where x represent the minutes and y represents the number of flashcards in x minutes
Solving (b): System of linear equation
Cindy:

per minute
Total number of flashcards (y) in x minutes is:



Ruben:
per minute
Total number of flashcards (y) in x minutes is:



Solution to Equations:
Time they have the same amount.
To do this, we
expressions
i.e.

Collect Like Terms


Number of cards they have at that time.
Here, we simply substitute 14 for x in any of the equations.



or




We have an arithmetic sequence with
<span>a0 = 1st 3-digit number divisible by 13 </span>
<span>a0 = 104 </span>
<span>d = 13 (why?) </span>
<span>last term is largest divisible by 13 = 988 </span>
<span>how many terms? (988-104)/13 + 1 = 69 </span>
<span>S = 69/2(104+988) = 37674</span>
Well yeah it depends on the kids age and the parents age to