SOLUTION: Can someone help me with this problem? I'm not good with algebra at all. The function D (t) = 11t to the second power – 130t gives the distance a car going a certain speed wil

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Question 418144: Can someone help me with this problem? I'm not good with algebra at all.

The function D (t) = 11t to the second power – 130t gives the distance a car going a certain speed will skid in t seconds. Find the time it would take for the car to skid 170 feet.
The time to skid 170 feet is __________ seconds.
(Round to the nearest tenth.)
Answer by edjones(8007) About Me  (Show Source):
You can put this solution on YOUR website!
11t^2-130t=170
11t^2-130t-170=0
t=13 seconds
.
Ed
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Solved by pluggable solver: SOLVE quadratic equation with variable
Quadratic equation ax%5E2%2Bbx%2Bc=0 (in our case 11x%5E2%2B-130x%2B-170+=+0) has the following solutons:

x%5B12%5D+=+%28b%2B-sqrt%28+b%5E2-4ac+%29%29%2F2%5Ca

For these solutions to exist, the discriminant b%5E2-4ac should not be a negative number.

First, we need to compute the discriminant b%5E2-4ac: b%5E2-4ac=%28-130%29%5E2-4%2A11%2A-170=24380.

Discriminant d=24380 is greater than zero. That means that there are two solutions: +x%5B12%5D+=+%28--130%2B-sqrt%28+24380+%29%29%2F2%5Ca.

x%5B1%5D+=+%28-%28-130%29%2Bsqrt%28+24380+%29%29%2F2%5C11+=+13.006407361557
x%5B2%5D+=+%28-%28-130%29-sqrt%28+24380+%29%29%2F2%5C11+=+-1.18822554337521

Quadratic expression 11x%5E2%2B-130x%2B-170 can be factored:
11x%5E2%2B-130x%2B-170+=+11%28x-13.006407361557%29%2A%28x--1.18822554337521%29
Again, the answer is: 13.006407361557, -1.18822554337521. Here's your graph:
graph%28+500%2C+500%2C+-10%2C+10%2C+-20%2C+20%2C+11%2Ax%5E2%2B-130%2Ax%2B-170+%29