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Mathematics 19 Online
zarkam21:

help

zarkam21:

1 attachment
Vocaloid:

|dw:1513275163598:dw| try to compare what's going on in the function to the table

Vocaloid:

for example, y = x^2 - 5 looks like y = x^2 - c which means a shift down by c units so what happens to the graph of x^2 to get x^2 - 5?

Vocaloid:

"f(x) - c is the graph of f(x) shifted down by c units" "x^2 - 5 is the graph of ___ shifted down by __ units" try filling in the blanks

zarkam21:

f(x) 5

Vocaloid:

should be "x^2 shifted down by 5" but you're starting to get the idea ^^

Vocaloid:

try to apply a similar line of reasoning to y = -2x^2 using row 5 and row 7 of the table

Vocaloid:

|dw:1513275569852:dw|

Vocaloid:

using row 5: "the graph of -f(x) is the graph of f(x) reflected across the x-axis" now compare this to what is in the problem y = -x^2 is the graph of ___ reflected across the ___-axis try and fill in the blanks

zarkam21:

f(x) x

Vocaloid:

|dw:1513276001509:dw|

Vocaloid:

now, use row 7 to figure out how multiplying x^2 by 2 changes the function

zarkam21:

umm its reflected?

Vocaloid:

|dw:1513276199016:dw|

zarkam21:

oh okay its stretched

Vocaloid:

now let's put everything together "the graph of y = -2x^2 is the graph of x^2 stretched vertically by a factor of __ and reflected across the __-axis" try filling in the blanks

zarkam21:

y axis and factor of 2?

zarkam21:

I think :/

Vocaloid:

|dw:1513276586156:dw| refer to our earlier statements

zarkam21:

f(x) x^2

Vocaloid:

the factor is 2 the reflection is across x-axis "the graph of y = -2x^2 is the graph of x^2 stretched vertically by a factor of 2 and reflected across the x-axis"

Vocaloid:

keep in mind your description should mention x^2 not just the generic f(x)

zarkam21:

OH I think I understand a little now

Vocaloid:

now use row 4 to figure out what transformation is being applied to x^2 to get |dw:1513276720205:dw|(x-5)^2

zarkam21:

shift to the right?

zarkam21:

@Vocaloid

Vocaloid:

Good but how many units is it being shifted?

zarkam21:

5?

Vocaloid:

Excellent See if you can work out d using the table

zarkam21:

Sorry wwas on break, if you do not mind can we still continue ? =)

zarkam21:

@563blackghost @Shadow

zarkam21:

@Vocaloid

zarkam21:

would D be a stretch?

zarkam21:

@Vocaloid

zarkam21:

well by -3

Vocaloid:

horizontal or vertical? when you consider stretches and shrinks ignore the negative sign because we account for that with reflection

Vocaloid:

|dw:1514987990504:dw|

Vocaloid:

*** should be a shrink since it's inside the parentheses and its > 1

Vocaloid:

|dw:1514988174150:dw|

Vocaloid:

now, instead of the generic "a" look at your problem and see what number you would replace "a" with

zarkam21:

3

Vocaloid:

good, now put everything together y = (-3x)^2 is a horizontal shrink by a factor of 1/3 now consider the negative sign

Vocaloid:

|dw:1514988456667:dw|

zarkam21:

\(\color{#0cbb34}{\text{Originally Posted by}}\) @Vocaloid good, now put everything together y = (-3x)^2 is a horizontal shrink by a factor of 1/3 now consider the negative sign \(\color{#0cbb34}{\text{End of Quote}}\)

zarkam21:

so this would be the answer, or are we not done yet

Vocaloid:

"now consider the negative sign"

zarkam21:

alright

Vocaloid:

|dw:1514988540829:dw|

Vocaloid:

add this statement to the answer and then you're done

zarkam21:

so reflect f(3)

Vocaloid:

across the y-axis, yes

Vocaloid:

reflect f(x) not f(3)

Vocaloid:

f(3) is a point not a graph

zarkam21:

okay so the overall answer would be y = (-3x)^2 is a horizontal shrink by a factor of 1/3. Reflect f(3) over the y-axis.

Vocaloid:

actually they use y not f(x) so let's write it as "y = (-3x)^2 is a horizontal shrink of y = x^2 by a factor of 1/3 and a reflection of y across the y-axis" done

zarkam21:

Reflection of f(3) over the y-axis.**

zarkam21:

okay i sort of get it now

zarkam21:

you just match up the problem with the table you gave right

Vocaloid:

yeah, but also think about what is happening to the graph and try to visualize the transformations

zarkam21:

okay now lets try a

Vocaloid:

\(\color{#0cbb34}{\text{Originally Posted by}}\) @Vocaloid should be "x^2 shifted down by 5" but you're starting to get the idea ^^ \(\color{#0cbb34}{\text{End of Quote}}\) a is "y shifted down 5 units"

zarkam21:

would it be shift f(x) downward c units?

zarkam21:

oh okay

Vocaloid:

that's the correct line in the table but they want you to describe what is happening in the function given in the problem not the generic f(x) and c

zarkam21:

5 units are being shifted to the right?

Vocaloid:

be careful with the parentheses, since the -5 is not inside parentheses it is being applied to the whole function not just x, making it a shift down not right

zarkam21:

oh okay

Vocaloid:

|dw:1514988941034:dw|

zarkam21:

so if it would be in the parenthesis it would be right

zarkam21:

right and we are on the second one

Vocaloid:

yeah it would have to be (x-5)^2 to be a shift right

Vocaloid:

sure

zarkam21:

because it is being applied to the entire function

Vocaloid:

yes

zarkam21:

okay so it is being shifted down 5 units?

Vocaloid:

yes

zarkam21:

so the answer would be shifted down 5 units

Vocaloid:

yes

zarkam21:

okay now for b

zarkam21:

reflect f(x) in the y-axis?

Vocaloid:

that's part of it, there's one more transformation though (consider the 2 coefficient)

zarkam21:

um shrink f(x) vertically by a factor of a

Vocaloid:

|dw:1514989351889:dw| for stretches and shrinks you can disregard the negative sign when determining whether a > 1 or < 1

zarkam21:

okay so stretch

Vocaloid:

good, so it stretches it by 2 vertically and reflects across the x-axis = ans

Vocaloid:

*meant to correct you earlier about the axis of reflection whoops

Vocaloid:

|dw:1514989455947:dw|

zarkam21:

its alright

zarkam21:

now for c it would be shift f(x) to the right c units

Vocaloid:

good, so instead of c it's 5

zarkam21:

because everything falls inside the parenthesis

Vocaloid:

yup

zarkam21:

shift f(x) to the right 5 units

Vocaloid:

good ^^ they use "y" instead of f(x) though so I would just replace f(x) with y

zarkam21:

and there is no second transformation for this one right

Vocaloid:

nope that's it

zarkam21:

thank you so much

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