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4 years ago

12

A LOT OF POINTS!!!! Darnell's car used 8 gallons of gasoline to travel 340 miles. After a mechanic worked on the car, it used 7

gallons of gasoline to travel 350 miles. If the price of gasoline was approximately $4.00 per gallon, how much less, to the nearest cent per mile, did it cost to run the car after the mechanic worked on it? Please tell me the correct answer with the steps!! Whoever gives the answer with steps will be marked the BRAINLIEST!!!

2 answers:

Diano4ka-milaya [45]4 years ago

7 0

Cost before
8*4=32
32/340=0.0941

after
7*4=28
28/350=0.08 exactly

about 1 cent per mile cheaper

Anon25 [30]4 years ago

6 0

I think $1 went DOWN Hope this helps! :)

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Answer:

$y=-\dfrac{13}{49}x^2$

Step-by-step explanation:

The shape of an arch corresponds to a parabola.

the general equation for a parabola is:

$y=ax^2+bx+c$

we're given three coordinates: (-7,-13),(7,-13) and (0,0)

so we can plug these values in the general equation to make 3 separate equations:

(x,y) = (-7,-13)

$-13=a(-7)^2+b(-7)+c$

$49a-7b+c=-13$

(x,y) = (7,-13)

$-13=a(7)^2+b(7)+c$

$49a+7b+c=-13$

(x,y) = (0,0)

$0=a(0)^2+b(7)+c$

$c=0$

so we have three equations. and we can solve them simultaneously to find the values of a,b, and c.

we've already found c = 0, let's use substitute it to other equations.

$49a-7b+c=-13\quad\Rightarrow\quad49a-7b=-13$

$49a+7b+c=-13\quad\Rightarrow\quad49a+7b=-13$

we can solve these two equation using the elimination method, by simply adding the two equations

$\quad\quad49a-7b=-13\\+\quad49a+7b=-13$

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$\quad\quad 98a=-26$

$\quad\quad a=-\dfrac{13}{49}$

Now we can plug this value of a in any of the two equations.

$49a-7b=-13$

$49\left(-\dfrac{13}{49}\right)-7b=-13$

$-13-7b=-13$

$-7b=0$

$b=0$

We have the values of a,b, and c. We can plug them in the general equation to find the equation of the arch.

$y=\left(-\dfrac{13}{49}\right)x^2+0x+0$

$y=-\dfrac{13}{49}x^2$

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This our equation of the arch!

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Answer:

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Step-by-step explanation:

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Answer:

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