The area in square feet of a rectangular field is x^2-160x+6300. the width, in feet, is x-70. what is the length in feet? would really appreciate if you explain, i need to know this for my final!

To find the answer, it is best to use formulas.  Area is mentioned, so lets use the formula for area, A=lw. Plugging in, you get  .  While this might look confusing, it is easier than you think: divide both sides by (x-70) for  .  From here, try factoring the top: there is a -90 difference between -70 and -160 and luckily -70 times -90 equals 6300.  So, your equation should look like  .  You can eliminate (x-70) from the top and bottom, so you should get l=x-90 .  Since there is no way to find x, x-90 is your length.