Question 339751
An apple orchard that contains 90 trees.
 The number of trees in each row is 3 more than twice the number of rows.
 Find the number of rows and the number of trees per row
:
Let r = number of rows
Let n = number in each row
Then 
r * n = 90
:
It also says,"The number of trees in each row is 3 more than twice the number of rows."
the equation for this statement:
n = 2r + 3
:
In the 1st equation, replace n with (2r+3) and you have
r*(2r+3) = 90
2r^2 + 3r = 90
2r^2 + 3r - 90 = 0; a quadratic equation
Factors to
(2r + 15)(r - 6) = 0
the positive solution is all we want here
r = 6 rows
then
n = {{{90/6}}}
n = 15 in each row
:
:
Confirm this with n = 2r + 3
15 = 2(6) + 3