Question 184159
Let x=number of rows to start with
x-6=new number of rows after the plants are redistributed
Then 180/x=number of plants per row
Add 40 more plants to each row and we have
(180/x)+40=(180+40x)/x---- new number of plants per row
(new # plants/row)(new # rows)=180
(180+40x)/x * (x-6)=180 or
(x-6)(180+40x)=180x  expand left side using FOIL
180x+40x^2-1080-240x=180x subtract 180x from each side
40x^2-240x-1080=0  divide each term by 40
x^2-6x-27=0----quadratic in standard form and it can be factored
(x-9)(x+3)=0
Disregard negative value for x;  rows are positive
x=9---------------number of rows to start with

CK
180/9=20 plants/row
20+40=60 plants/row
60*(9-6)=180
180=180

Hope this helps---ptaylor