Question

@tcarroll010 can you help me with 4 and 5 of this....

Answer 1

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

Answer 2

# 4

D = b^2 - 4ac

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

D = ???

Answer 3

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

Answer 4

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.

Answer 5

im confused

Answer 6

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

Answer 7

I think phi has got you covered

Answer 8

hmmm....???

Answer 9

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

Answer 10

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?

Answer 11

i have that part i need number 5

Answer 12

what did you get for a, b and c

Answer 13

wait what?? like for the explanation part??

Answer 14

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

Answer 15

??

Answer 16

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?

Answer 17

a=0.05
b=1x
c=1

Answer 18

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

Answer 19

1^2-4(0.05)(1)

Answer 20

.8

Answer 21

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

Answer 22

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

Answer 23

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

Answer 24

@phi ??

Answer 25

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?

Answer 26

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

Answer 27

@phi ?? like that??

Answer 28

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!)

Answer 29

yea i know it is a typo the graph is wrong

Answer 30

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

Answer 31

wait i am confused

Answer 32

which part?

Answer 33

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

Answer 34

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?

Answer 35

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 :/

Answer 36

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

Answer 37

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

Answer 38

in Q2, the -10 become +10


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

Answer 39

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

Answer 40

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

Answer 41

in Q3, your x-intercepts should be positive

Answer 42

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

Answer 43

ok thanks for all that :D

Answer 44

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

Answer 45

@phi