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

- anonymous

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

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- anonymous

##### 1 Attachment

- anonymous

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

- jim_thompson5910

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

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## More answers

- anonymous

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

- 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.

- anonymous

im confused

- phi

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

- anonymous

I think phi has got you covered

- anonymous

hmmm....???

- anonymous

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

- 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?

- anonymous

i have that part i need number 5

- phi

what did you get for a, b and c

- anonymous

wait what?? like for the explanation part??

- anonymous

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

- anonymous

??

- 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?

- anonymous

a=0.05
b=1x
c=1

- 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

- anonymous

1^2-4(0.05)(1)

- anonymous

.8

- 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

- anonymous

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

- anonymous

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

- anonymous

@phi ??

- 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?

- anonymous

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

- anonymous

@phi ?? like that??

- 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!)

- anonymous

yea i know it is a typo the graph is wrong

- 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

- anonymous

wait i am confused

- phi

which part?

- anonymous

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

- 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?

- anonymous

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 :/

- phi

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

- anonymous

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

- phi

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

- phi

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

- phi

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

- phi

in Q3, your x-intercepts should be positive

- phi

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

- anonymous

ok thanks for all that :D

- anonymous

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

- anonymous

@phi

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