2l + 2w = p
If you already have perimeter and length, you can use this formula to solve for width.
Answer:

Step-by-step explanation:
Let us consider the equation 
For a quadratic equation in a standard form,
, the axis of symmetry is the vertical line
.
Here in this case we have, 
Putting the values we get,

We can see that the axis of symmetry is x=3 and the graph is giving minimum at x=3.
Therefore, the required equation is
. Refer the image attached.
A² + 2ab + b² ; Solve when a=10 & b=50
Simply plug in 10 for a and 50 for b in our given equation :)
(10)² + 2(10)(50) + (50)²
Simplify.
100 + 20(50) + 2500
Simplify.
(100 + 2500) + 1000
Simplify.
2600 + 1000
Simplify.
3600
Hope I helped! :)