Solution to quadratic equation

[zjb0417]

I have three problems left on an asignment that I am having difficulty working out. The first two are quadratice equations which I must use the graphing method to solve one and factoring to solve the other.

1. 3x2 + 11x – 20 = 0 (The 3x2 means 3x squared)
2. 3x2 – x – 1 = 0 (The 3x2 means 3x squared)

The last problem has me completely stumped - A school bus holds 57 students but is only 40% full. How many students are on the bus?

I am being asked to explain why the answer of 22.8 students is unreasonable,give a reasonable answer in its place,
explain why your answer is more reasonable.

I can't see why the answer of 22.8 would not be resonable and how any other answer would be given. If the bus holds 57 students (100%) then 40% of that would be 22.8 students.

Any help would be greatly appreciated....

 

[Vertciel]

Hello there,

1. 3x2 + 11x – 20 = 0 (The 3x2 means 3x squared)
2. 3x2 – x – 1 = 0 (The 3x2 means 3x squared)
3. The last problem has me completely stumped - A school bus holds 57 students but is only 40% full. How many students are on the bus?

---

To graph quadratic equations, I would find the vertex of this quadratic equation, and then substitute reasonable, convenient values from there for graphing.

1. \(\displaystyle 3x^2 + 11x - 20 = 0\)

\(\displaystyle (3x - 4)(x + 5) = 0\)

\(\displaystyle x = -5, 4/3 or 1.333\)

2. \(\displaystyle 3x^2 - x - 1 = 0\)

This equation cannot be factored.

3. You cannot have 22.8 students as an answer because there's no such thing as 22 and three-quarters of a human (I certainly hope not...)! Therefore, I would give 22 as an answer because it is possible to have 22 students, but not to have 3/4s of a student. If you're wondering about 23, it would not be a reasonable answer because your mathematical answer is 22.8 and 23 > 22.8.

Hope this helps!