A quadratic equation given roots is solved by using the relation
from the question,
sum of the root will be
and also, product of the roots will
be
now substituting the sum of roots and product of roots into the equation
as the quadratic equation for the root 3/4 and -4
Answer:
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Explanation:
r = number of red pens
4r = cost of buying r red pens
example: if r = 10, then 4r = 4*10 = 40 is the total cost of buying 10 red pens
If John buys r red pens, then he must buy 20-r black pens so that r and 20-r add to 20.
John buys 20-r black pens, and at $5 each, so it will cost 5(20-r) dollars for just the black pens alone.
In total, John spends 4r + 5(20-r) dollars for all the pens (red & black)
We want $92 be the most he spends. This is the ceiling or highest value possible.
Therefore,
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Extra info:
If you want to solve for r, then
distribute
add r to both sides
subtract 92 from both sides
So John must buy at least 8 red pens. The most he can buy is 20 red pens since he wants 20 pens total.