## swin2013 3 years ago Why don't I have to factor out the (1+h)^2? on problem 2, page 2? http://www.math.wisc.edu/~hernande/Teaching/UM/Math115Sec011Winter2011/Quizzes/Quiz3/Solution/Quiz3Sol.pdf

1. swin2013

yea but i don't need to square 1+h because why? lol

2. swin2013

usually i have to square it... that's why. especially for a slope problem.

3. phi

I don't understand the question. you are asked to find the average velocity = distance/time the distance traveled in the time between 1 and 1+h (with h=0.1) is 4(1.1)^2 +3 - ( 4*1^2 +3) 4*1.21 + 3 -4 -3 4.84 -4 0.84 the time interval is 0.1 sec, so velocity is 0.84/0.1 = 8.4 sec

4. phi

in other words, you do square (1+h)

5. swin2013

but when i squared (1+h), the 4's and 3's cancel. i get 8.04 when the answer should be 8.4 m/s

6. phi

in each case, you find how far the particle got by time step 1. Then find where it is at time step 1+h. The difference between those two distances is how far it moved in h secs.

7. phi

but when i squared (1+h), the 4's and 3's cancel. i get 8.04 when the answer should be 8.4 m/s for case (i), with h = 0.1 1+h is 1.1 1.1*1.1= 1.21 4*1.21= 4.84 subtract 4 0.84 divide by 0.1 to get 8.4 you must have made a mistake doing 1.1 * 1.1 ??

8. phi

I am not sure how you did your calculation, but you have a "bug" in it, so it would be good to figure out where you are going wrong...

9. swin2013

\[4(h ^{2}+2h+1) +3-4(1)^{2}-3\] since t =1?

10. swin2013

and t = 1+h

11. phi

yes. that looks ok. then 4h^2 +8h +4 +3 -4 -3 = 4h^2+8h if we divide by h (to get velocity) 4h+8 with h=0.1 this is 4*0.1+8 = 0.4+8= 8.4 perfect!

12. swin2013

ok that's where i went wrong. i factored out 4h so it would be 4h ( h^2 +2) and canceled out the h's so it would be left with 4(h^2+2)

13. phi

if you factor out 4h, it should be 4h(h+2) and 4(h+2) after dividing by h

14. swin2013

yea that's my mistake... i left the squared. thanks :)

15. swin2013

i can't believe it was that miniscule

16. phi

so close....

17. swin2013

i know! such a tiny mistake could cost me an answer by one decimal place -_-

18. phi

sometimes it just doesn't work out...good luck!