Help

[pggirl]

I think I know the answer to this problem but when I put it in an algebric equation. I don't know what to do next. The problem states: The length of a rectangle is 9 more than its width.
If the area is 90 sqft find the dimensions. Am I right when I express this equation as: X(X+9)=90. If yes please help me to understand how I find the dimensions.

 

[wjm11]

I think I know the answer to this problem but when I put it in an algebric equation. I don't know what to do next. The problem states: The length of a rectangle is 9 more than its width.
If the area is 90 sqft find the dimensions. Am I right when I express this equation as: X(X+9)=90. If yes please help me to understand how I find the dimensions.

Great start. What you have is a quadratic equation. What methods do you know for solving a quadratic? Start by expanding, then rearranging terms so that you have 0 on one side:

x(x+9)=90
x^2 + 9x = 90
x^2 + 9x - 90 = 0

Now apply the quadratic formula to solve for x. x is your width. x + 9 is your length.

 

[Deleted member 4993]

You'll get two solutions for 'x' by solving the quadratic equation. One will give you a positive 'x' - and other a negetive 'x'.

Negetive (length) 'x' is physically impossible - hence you'll discard it and choose the positive answer to be your correct answer for width.