SOLUTION: i have a worded problem that i cannot do. it goes like this: A triangles base is x cm and the height is 3cm shorter than the base if the area is 20 what is the value of x. I have

Algebra ->  Quadratic Equations and Parabolas  -> Quadratic Equations Lessons  -> Quadratic Equation Lesson -> SOLUTION: i have a worded problem that i cannot do. it goes like this: A triangles base is x cm and the height is 3cm shorter than the base if the area is 20 what is the value of x. I have      Log On


   

Question 14834: i have a worded problem that i cannot do. it goes like this:
A triangles base is x cm and the height is 3cm shorter than the base if the area is 20 what is the value of x.
I have worked out the answer but i dont know how to get to it.
please help me
Answer by rapaljer(4671) About Me  (Show Source):
You can put this solution on YOUR website!
Let x = base of triangle
x-3 = height of triangle

Area = %281%2F2%29%2Ab%2Ah+=+20
%281%2F2%29%2Ax%2A%28x-3%29+=+20+

Multiply both sides by 2 to clear the fraction:
2%2A%281%2F2%29%2Ax%2A%28x-3%29+=+2%2A20
x%5E2+-+3x+=+40+

Quadratic equation, so set equal to zero:
x%5E2+-+3x+-+40+=+0
+%28x-8%29%28x%2B5%29+=+0
x=8 base
x-3= 5 height
Reject x=-5, since the base of a triangle cannot be negative.

R^2 at SCC