Very Hard Quadtratic Equation

ebaines · Nov 5, 2007, 12:46 PM

You start with a sheet that's 40 x 30. When you cut out the 4 corners, the dimensions of the base at the center that's left will be (40-2x) by (30-2x). You want that to equal 900, so:

(40-2x) * (30-2x) = 900.

Now multiply this out into the common form for quadratic equations: ax^2 + bx+ c=0, and solve, using the quadratic formula.

Slavce · Nov 5, 2007, 01:05 PM

I got -15 and -20 but in the answers it says 2.3

ebaines · Nov 5, 2007, 01:33 PM

Multiply out the equation I gave you, and you get:

$ 4x^2 -140x+300 = 0 $

Did you get the same thing?

Then divide through by 4 to get:

$ X^2 - 35x + 75=0 $

And solve using the quadratic equation:

$ X = \frac {35 \pm sqrt {35^2 - 4\cdot1\cdot 75}} 2 $

Which gives you x = 2.3 or 32.7 Only one of these answers makes sense, so that's the correct one.

terryg752 · Nov 5, 2007, 04:29 PM

Let the side of squares cut = x

Then the base has sides: 40 - 2x and 30 - 2x

Area of base = 900

(40 -2x) (30 - 2x) = 900

1200 - 140 x + 4x^2 = 900

4 x^2 - 140 x +300 = 0

X^2 - 35 x + 75 = 0

Then proceed as usual

Very Hard Quadtratic Equation

Add your answer here.

Check out some similar questions!