Thread: help with quadratic word problems?

1. help with quadratic word problems?

ladder location. A ladder leaning against the wall of a building is 13ft long. The distance from the building to the bottom of the ladder is 7ft less than the distance (d) to the top of the ladder. Find the distance d to the top of the ladder and the distance from the building to the bottom of the ladder.

can someone solve this using a quadratic equation and be able to tell me the distance to top of ladder and distance from building?

and another one is

Rectangular envelope. The length of a rectangular envelope is 4 in greater than its width. The area of the envelope is 96 in^2. Find the length and the width of the envelope using a quadratic equation.

Thx in advanced. im lost with these word problems

2. For the first one, using Pythagorus' Theorem, you have:

$13^2=d^2+(d-7)^2$

and for second one you should get:

$96=w(w+4)$

Do you need help from there?

3. yes i do, also i thought it was suspose to be in the form of

4. Originally Posted by wonderd
yes i do, also i thought it was suspose to be in the form of
You're meant to use algebraic manipulation (such as the binomial theorem) to get it into that form

$d^2+(d-7)^2 = 13^2$

$d^2+d^2-14d+49=169$

$2d^2-14d-120=0$

$d^2-7d-60=0$

(Hint: This one factorises)

5. can i just take and use the quadratic formula to get the 2 answers?

6. Originally Posted by wonderd
can i just take and use the quadratic formula to get the 2 answers?
You can

7. what would be in the form of

8. Not quite:

$96=w(w+4)$

$96=w^2+4w$

$w^2+4w-96=0$

Have a look here: http://www.purplemath.com/modules/index.htm under the "Intermediate Algebra Topics" for more info on how to expand, factorise, and solve quadratic equations.