Math
posted by Michelle on .
I'm doing some word problems on finding the areas of rectangles, its just like all complicated. I don't understand how to do them. For example:
A square field had 3 m added to its length and 2m added to its width. The area is 90 m2(squared). Find the length of a side of the original field.
So first you get (x+3)(x+2)=90, right?
then you get x2+5x+6=90
then x2+5x=84
How do you go on? How do you figure out x? I don't get it! I have other problems like those, could you tell me how to figure out a problem with x2 and something x = a number in general? Please help!

Take your step:
x^2 + 5x + 6 = 90
Now:
x^2 + 5x  84 = 0
Factor by inspection or use the quadratic formula to solve for x.
A hint is what two factors of 84 differ by 5?