Swageraid32 3 years ago @tcarroll010 can you help me with 4 and 5 of this....

1. Swageraid32

2. Swageraid32

those are my last two please........... ;/

3. jim_thompson5910

# 4 D = b^2 - 4ac D = (1)^2 - 4(0.05)(1) D = ???

4. shyLove98

I'm sorry. I don't know any of this. I tried. I'm really really really sorry. :(((

5. phi

if you have a the equation of a parabola in standard form: y= ax^2 + bx +c you match up the coefficients of your equation with a, b, and c then use those numbers for a, b, and c in the formula discriminant= b^2 -4ac jim_t already did most of the work for you.

6. Beautiful_Lier96

im confused

7. phi

y= 0.05 x^2 + 1x + 1 is your equation

8. evergirl

I think phi has got you covered

9. Swageraid32

hmmm....???

10. Swageraid32

you mean that is how i do the quadratic part??

11. phi

we are doing question 4. They want to know the discriminant (of your quadratic equation) I assume they mean the equation they give in question 1 To find the discriminant we first do step 1: first step: pattern match y= 0.05 x^2 + 1x + 1 y= a x^2 +b x + c what is a,b, and c?

12. Swageraid32

i have that part i need number 5

13. phi

what did you get for a, b and c

14. Swageraid32

wait what?? like for the explanation part??

15. Swageraid32

D = (1)^2 - 4(0.05)(1)

16. Swageraid32

??

17. phi

I see you copied Jim's answer To find the discriminant we first do step 1: first step: pattern match y= 0.05 x^2 + 1x + 1 y= a x^2 +b x + c what is a,b, and c?

18. Swageraid32

a=0.05 b=1x c=1

19. phi

almost, b is just 1 (we only want the numbers. a= 0.05, b=1 , c=1 step 2: replace the letters a, b, and c in b^2 - 4ab with the numbers you just found (remember b^2 is short for b*b 4ab is short for 4*a*b * means multiply

20. Swageraid32

1^2-4(0.05)(1)

21. Swageraid32

.8

22. phi

now what is 1^2 ? 1*1 = 1 4*0.05 is 0.2 0.2*1 is 0.2 so 1- .2 = 0.8 the discriminant is 0.8

23. Swageraid32

ok i get that thanks for actually working with me and not giving just the answer :D

24. Swageraid32

so could you assist me in #5 as well??

25. Swageraid32

@phi ??

26. phi

For 5, the quadratic formula is $x=\frac{−b±\sqrt{b^2−4ac}}{2a}$ notice that the stuff inside the square root is the "discriminant", which you already figured out is 0.8 you also know what a, b and c are. So replace the letters with numbers what do you get?

27. Swageraid32

a=0.05, b=1, c=1 $x=\frac{−1±\sqrt{1^2- 4\times0.05\times1}}{2\times0.05}$

28. Swageraid32

@phi ?? like that??

29. phi

I just noticed that the equation you have from question 1 should be y= 0.05x^2 -x +1 notice that b is -1 (not +1) this changes your answers (gack!)

30. Swageraid32

yea i know it is a typo the graph is wrong

31. phi

if we use b= -1 we get $x= \frac{1 ± \sqrt{0.8}}{0.1}= 10±\sqrt{80} = 10± 4\sqrt{5}$ you get two answers x= 10+4sqrt(5) and x= 10-4sqrt(5) these are where the graph crosses the x-axis

32. Swageraid32

wait i am confused

33. phi

which part?

34. Swageraid32

the part like so i need to switch it to a -1?

35. phi

It's your call. The question says find the equation, from the graph. Did you find the equation from the graph? If so, you got it wrong?

36. Swageraid32

o wow no i used the graph that was provided on the graph ;( that means i have to go back and do this all again :/

37. phi

Q1 general equation is y=0.05 x^2 -x +1 vertex form is 0.05(x-10)^2 - 4

38. Swageraid32

so that means its this? y= 0.05 x^2 -1x + 1

39. phi

in Q2, the -10 become +10 so that means its this? y= 0.05 x^2 -1x + 1 Yes

40. phi

in Q2, the domain are all valid x's in this case, -inf to +infinity

41. phi

in Q2, the range is all y values. from the graph, you see y is always bigger than -4

42. phi

in Q3, your x-intercepts should be positive

43. phi

in Q4, b is -1 not +1, but it won't change the discriminant calculation.

44. Swageraid32

ok thanks for all that :D

45. Swageraid32

i do need your help again though i mean how are you supposed to find the domain and range? @phi

46. Swageraid32

@phi