Last question on my ! goran drove to the mountains last weekend. there was heavy traffic on the way there, and the trip took 12 hours. when goran drove home, there was no traffic and the trip only took 8 hours. if his average rate was 20 miles per hour faster on the trip home, how far away does goran live from the mountains? do not do any rounding.

Givens

Slower car

r = r

t = 12 hours

d = ?

Faster car

r = r + 20

t = 8 hours

d = ?

It doesn't matter what the exact distance is. You just have to know that the 2 distances are equal ie going to the mountains from his home is the same distance as going from the mountains to his home.

d = r * t

r * 12 hours = (r + 20)* 8 hours.   Remove the brackets on the right

r*12 = 8r + 20*8

r*12 = 8*r + 160

r*12 - 8r = 8r - 8r + 160

4r = 160

r = 40 miles / hour

Slower Ride determines the distance.

d = r*t

d = 40 * 12

d = 480

Check

Use the faster rate (r + 20) = 40 + 20 = 60 mph

60 * 8 = 480. Both distances work out to be the same.

let's call the solutions x₁ = (5 - 2√7)/3 and x₂ = (5 + 2√7)/3

then the equation is (x-x₁)(x-x₂) = 0

if you fill that in you get a lot of numbers which you can recognize as ax²+bx+c=0.

step-by-step explanation:

you can see that a=1 (there is just an x²)

b = (-5 -2√7 + 2√7 - 5)/3 = -10/3

c = -2√7)/3 ) * (-5+2√7)/3) = -1/3

so your answer is 3x^2 – 10x – 1 = 0