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3 years ago

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7. Using k as the constant of proportionality, write an equation that expresses: Z varies jointly as x and y. If Z = 24 when x =

3 and y = 4, find Z when x = 5 and y = 6. (show steps)

1 answer:

VARVARA [1.3K]3 years ago

6 0

Answer:

60

Step-by-step explanation:

"z varies jointly as x and y" can be expressed algebraically as z = kxy, where k is the constant of proportionality.

Given: z = 24 when x = 3 and y = 4, then 24 = k(3)(4), or 24 = 12k.

The const. of prop. must then be k = 2.

So now we have the specific relationship z = 2xy.

If x = 5 and y = 6, then z = 2(5)(6) = 60.

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find the centre and radius of the following Cycles 9 x square + 9 y square +27 x + 12 y + 19 equals 0

Citrus2011 [14]

Answer:

Radius: $r =\frac{\sqrt {21}}{6}$

$Center = (-\frac{3}{2}, -\frac{2}{3})$

Step-by-step explanation:

Given

$9x^2 + 9y^2 + 27x + 12y + 19 = 0$

Solving (a): The radius of the circle

First, we express the equation as:

$(x - h)^2 + (y - k)^2 = r^2$

Where

$r = radius$

$(h,k) =center$

So, we have:

$9x^2 + 9y^2 + 27x + 12y + 19 = 0$

Divide through by 9

$x^2 + y^2 + 3x + \frac{12}{9}y + \frac{19}{9} = 0$

Rewrite as:

$x^2 + 3x + y^2+ \frac{12}{9}y =- \frac{19}{9}$

Group the expression into 2

$[x^2 + 3x] + [y^2+ \frac{12}{9}y] =- \frac{19}{9}$

$[x^2 + 3x] + [y^2+ \frac{4}{3}y] =- \frac{19}{9}$

Next, we complete the square on each group.

For $[x^2 + 3x]$

1: Divide the $coefficient\ of\ x\ by\ 2$

2: Take the $square\ of\ the\ division$

3: Add this $square\ to\ both\ sides\ of\ the\ equation.$

So, we have:

$[x^2 + 3x] + [y^2+ \frac{4}{3}y] =- \frac{19}{9}$

$[x^2 + 3x + (\frac{3}{2})^2] + [y^2+ \frac{4}{3}y] =- \frac{19}{9}+ (\frac{3}{2})^2$

Factorize

$[x + \frac{3}{2}]^2+ [y^2+ \frac{4}{3}y] =- \frac{19}{9}+ (\frac{3}{2})^2$

Apply the same to y

$[x + \frac{3}{2}]^2+ [y^2+ \frac{4}{3}y +(\frac{4}{6})^2 ] =- \frac{19}{9}+ (\frac{3}{2})^2 +(\frac{4}{6})^2$

$[x + \frac{3}{2}]^2+ [y +\frac{4}{6}]^2 =- \frac{19}{9}+ (\frac{3}{2})^2 +(\frac{4}{6})^2$

$[x + \frac{3}{2}]^2+ [y +\frac{4}{6}]^2 =- \frac{19}{9}+ \frac{9}{4} +\frac{16}{36}$

Add the fractions

$[x + \frac{3}{2}]^2+ [y +\frac{4}{6}]^2 =\frac{-19 * 4 + 9 * 9 + 16 * 1}{36}$

$[x + \frac{3}{2}]^2+ [y +\frac{4}{6}]^2 =\frac{21}{36}$

$[x + \frac{3}{2}]^2+ [y +\frac{4}{6}]^2 =\frac{7}{12}$

$[x + \frac{3}{2}]^2+ [y +\frac{2}{3}]^2 =\frac{7}{12}$

Recall that:

$(x - h)^2 + (y - k)^2 = r^2$

By comparison:

$r^2 =\frac{7}{12}$

Take square roots of both sides

$r =\sqrt{\frac{7}{12}}$

Split

$r =\frac{\sqrt 7}{\sqrt 12}$

Rationalize

$r =\frac{\sqrt 7*\sqrt 12}{\sqrt 12*\sqrt 12}$

$r =\frac{\sqrt {84}}{12}$

$r =\frac{\sqrt {4*21}}{12}$

$r =\frac{2\sqrt {21}}{12}$

$r =\frac{\sqrt {21}}{6}$

Solving (b): The center

Recall that:

$(x - h)^2 + (y - k)^2 = r^2$

Where

$r = radius$

$(h,k) =center$

From:

$[x + \frac{3}{2}]^2+ [y +\frac{2}{3}]^2 =\frac{7}{12}$

$-h = \frac{3}{2}$ and $-k = \frac{2}{3}$

Solve for h and k

$h = -\frac{3}{2}$ and $k = -\frac{2}{3}$

Hence, the center is:

$Center = (-\frac{3}{2}, -\frac{2}{3})$

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blsea [12.9K]

Answer:n= 1/3d - 2/3m

Step-by-step explanation:

d=2m+3n

Step 1: Flip the equation.

2m+3n=d

Step 2: Add -2m to both sides.

2m+3n+−2m=d+−2m

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Hope this helps!

Plz name brainliest if possible.

1jaiz4 and 1 more users found this answer helpful

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Answer

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maxtext75

Helping Hand

15 answers

26 people helped

Answer:

n = d - 2m

3*

Step-by-step explanation:

First we want to get n alone on one side, so we should subtract 2m from both side;

d = 2m + 3n

3n = d - 2m

Now to get n by itself, we need to divide by 3 from both sides;

3n = d - 2m

n = d - 2m

3*

*Pretend there is a fraction bar between d - 2m and 3

Step-by-step explanation:

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Lisa and Bill made 60 magnets for a craft fair. They sold about 55% of the magnets. Lisa says they sold about 30 magnets. Bill s

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Answer:

Step-by-step explanation:

The total number of magnets that Lisa and Bill made for the craft fair is 60.

They sold about 55% of the magnets. The number of magnets that they sold would be about

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If Lisa says that they sold about 30 magnets, she is correct because if we round off 33 to the nearest ten, it would be 30 magnets.

If Bill says that they sold about 36 magnets, he is wrong because if we round off 36 to the nearest ten, it would be 40 magnets.

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