Math, Quadratics
posted by Kelly .
Adam has a hockey rink in his backyard. The current dimensions are 10m by 20m. Adam wants to have a hockey tournament and needs to double the area of his hockey rink. How much must Adam increase each dimension if he wants to increase them the same amount?

Math, Quadratics 
Mac
Current area = 200m2 [10m x 20m]
New area = 400m2 [10y x 20y]
So, 400 = 200y2
So, y2= 2
So, y = 1.41
So, each side must be increased by a factor 0f 1.41 times.
I this correct or do they mean add the same length to each side? 
Math, Quadratics 
Damon
same to each
(10+x)(20+x) = 400
200 + 30 x + x^2 = 400
x^2 + 30 x  200 = 0
x = [ 30 +/ sqrt(900 + 800) ]/2
x = [ 30 +/ 10 sqrt 17 ] /2
x = 15 +/ 5 sqrt 17
x = 5.62
new dimensions
15.62 * 25.62 = 400 ok 
Math, Quadratics 
Kelly
Hi Damon, I got the same answer as you up to the equation x^2 + 30x  200=0, but after that I don't understand what happened after that.. where does the 900 and 800 come form? and why you do divide by 2? thanks
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