Question

The monthly charges of two power companies supplying electricity to homes are given by these two equations, where y is the monthly charge in dollars for consumption of x units of electricity.
Company A: y = 10 + 2x2
Company B: y = 2.5x
At what usage (in number of units) will the monthly charges for both companies be equal?
12.5 units and 50.07 units
5 units and 20.2 units
12.5 units and 20.2 units
5 units and 50.07 units
The monthly charges will never be equal.

Answer 1

@jim_thompson5910

Answer 2

hey

Answer 3

The basic idea is to plug one of the equations into the other. Then solve for x.

y = 10 + 2x^2

2.5x = 10 + 2x^2

0 = 10 + 2x^2 - 2.5x

2x^2 - 2.5x + 10 = 0

now use the quadratic formula to solve for x. What do you get when you do so?

Answer 4

I am getting none of the answers

Answer 5

what results are you getting?

Answer 6

this formula?

Answer 7

correct, you use that formula

Answer 8

a=2

Answer 9

b=-2.5

Answer 10

correct :)
b=?
c=?

Answer 11

c=10?

Answer 12

yep, you then plug those values into the formula

Answer 13

yes
now try :)

Answer 14

x=-2.5±sqrt(2.5^2-4(2)(10))/2(2)?

Answer 15

yea

Answer 16

\[x=-2.5\pm \frac{ \sqrt{2.5^2-4(2)(10)} }{ 2(2) }\]

Answer 17

I hope that is it

Answer 18

focus on the stuff inside the square root: 2.5^2-4(2)(10)

Answer 19

what is that equal to?

Answer 20

-73.75

Answer 21

solve the equation

Answer 22

because that value is negative, this means that there are no real solutions for 2x^2 - 2.5x + 10 = 0. The two solutions are complex numbers. So that means the two graphs do NOT intersect at all telling us that the charges will never be equal no matter what x is

Answer 23

I knew it was something like that

Answer 24

Cool :)
complex no here

Answer 25

:)

Answer 26

All The best!

Answer 27

Yea I did get a complex number

Answer 28

didn't think it was what you all was looking for