A community has 10m x 25m swimming pool. They need to put a fence around the whole pool so that there is the same distance between the pool and the fence on all sides. The total fenced area needs to be 936 square meters.

Solve the equation (2x+10)(2x+25)=936 to find the distance between the pool and the fence. Then, fill in the statement below.

x=_ is a solution to the equation, and is the distance between the pool and the fence.
x=_ is a solution to the equation, but it does not make sense as the distance between the pool and the fence.

1 answer

To solve the equation \((2x + 10)(2x + 25) = 936\), we first expand the left side of the equation:

\[ (2x + 10)(2x + 25) = 4x^2 + 50x + 20x + 250 = 4x^2 + 70x + 250 \]

Now, we set this equal to 936:

\[ 4x^2 + 70x + 250 = 936 \]

Next, we want to set this equation to zero by subtracting 936 from both sides:

\[ 4x^2 + 70x + 250 - 936 = 0 \]

This simplifies to:

\[ 4x^2 + 70x - 686 = 0 \]

To make calculations easier, we can divide the entire equation by 2:

\[ 2x^2 + 35x - 343 = 0 \]

Now, we can use the quadratic formula, given by \(x = \frac{-b \pm \sqrt{b^2 - 4ac}}{2a}\), where \(a = 2\), \(b = 35\), and \(c = -343\).

First, we calculate the discriminant:

\[ b^2 - 4ac = 35^2 - 4 \cdot 2 \cdot (-343) = 1225 + 2744 = 3969 \]

Now, we take the square root of the discriminant:

\[ \sqrt{3969} = 63 \]

Now, we can substitute back into the quadratic formula:

\[ x = \frac{-35 \pm 63}{2 \cdot 2} = \frac{-35 \pm 63}{4} \]

This gives us two solutions:

  1. \(x = \frac{-35 + 63}{4} = \frac{28}{4} = 7\)
  2. \(x = \frac{-35 - 63}{4} = \frac{-98}{4} = -24.5\)

Now we have our two solutions:

  • \(x = 7\) (this is a valid solution since distance cannot be negative)
  • \(x = -24.5\) (this does not make sense as a distance)

Filling in the statement:

\(x = 7\) is a solution to the equation, and is the distance between the pool and the fence.
\(x = -24.5\) is a solution to the equation, but it does not make sense as the distance between the pool and the fence.