Dennis went cross-country skiing for 6 hours on Saturday. He skied 20 miles uphill and then 20 miles back downhill, returning to his starting point. His uphill speed was 5 mph slower than his downhill speed. What was Dennis’ speed going uphill and his speed going downhill?
20/r + 20/(r-5) = 6
r(r-5) * 20/r + r(r-5) * 20/(r-5) = r(r-5) * 6
20r-100+20r = 6r^2-30r
0 = 6r^2+10r+100
Confused with AC method:
6 x 100 = 600
30 * -20 = -600 (should it not be a positive, since the trinomial was positive?)
6r^2+30r-20r+100
6r(r+5)-20(r+5)
(6r-20)(r+5) = 0
Check:
6r-20 = 0
6r = 20
r = 20/-6 (doesn't work)
r + 5 = 0
r =-5
I have not completed the question, but will post another thread in regards to the final check.
20/r + 20/(r-5) = 6
r(r-5) * 20/r + r(r-5) * 20/(r-5) = r(r-5) * 6
20r-100+20r = 6r^2-30r
0 = 6r^2+10r+100
Confused with AC method:
6 x 100 = 600
30 * -20 = -600 (should it not be a positive, since the trinomial was positive?)
6r^2+30r-20r+100
6r(r+5)-20(r+5)
(6r-20)(r+5) = 0
Check:
6r-20 = 0
6r = 20
r = 20/-6 (doesn't work)
r + 5 = 0
r =-5
I have not completed the question, but will post another thread in regards to the final check.