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3 years ago

Graph and solve the following equation: 7r-15=r+27

Mathematics

1 answer:

svp [43]3 years ago

3 0

7r-15= r+27

Move +r to the other side. Sign changes from +r to -r.

7r-r-15= r-r+27

6r-15= 27

Move -15 to the other side. Sign changes from -15 to +15

6r-25+15= 27+15

6r= 42

Divide by 6 for 6r and 42

6r/6= 42/6

r= 7

Answer : r= 7

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The number of pencils sold varies directly as the cost.if 5 pencils cost $0.45,find the cost of 7 pencils.

vitfil [10]

7 times 0.45 divided by 5 and you get 0.63

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3 years ago

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Dylan has a 32-ounce coffee.He drinks 4 ounces. What is the percentage of ounces left of his coffee?

Semenov [28]

$32 \div 100 = 3.125 \\ \\ 3.125 \times 4 = 12.5 \\ \\ 100 - 12.5 = 87.5 \\ \\ 87.5$

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3 years ago

5/4 to 3/8 as a percent change

Digiron [165]

Well, what's the diffrence from 5/4 to 3/8?

$\bf \cfrac{5}{4}-\cfrac{3}{8}\qquad \stackrel{\textit{LCD is 8 clearly}}{\implies }\qquad \cfrac{10-3}{8}\implies \cfrac{7}{8}$

so, if we take 5/4 to be the 100%, what is 7/8 off of it in percentage anyway?

$\bf \begin{array}{ccll}
amount&\%\\
\text{\textemdash\textemdash\textemdash}&\text{\textemdash\textemdash\textemdash}\\
\frac{5}{4}&100\\\\
\frac{7}{8}&x
\end{array}\implies \cfrac{\quad \frac{5}{4}\quad }{\frac{7}{8}}=\cfrac{100}{x}\implies \cfrac{5}{4}\cdot \cfrac{8}{7}=\cfrac{100}{x}
\\\\\\
\cfrac{40}{28}=\cfrac{100}{x}\implies x=\cfrac{28\cdot 100}{40}$

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3 years ago

What is the equation of the line, in standard form, that passes through (4, -3) and is parallel to the line whose equation is 4x

Serggg [28]

Answer:

The equation of this line would be 4x + y = 13

Step-by-step explanation:

In order to find this equation we must first find the slope of the original line. To do this, we solve the original equation for y.

4x + y - 2 = 0

4x + y = 2

y = -4x + 2

The original slope (the coefficient of x) is -4, which means the new slope will also be -4 because parallel lines have the same slope. Now, we can use this slope along with the point in point-slope form to find the equation of the line. Just plug in the numbers and solve for the coefficient.

y - y1 = m(x - x1)

y + 3 = -4(x - 4)

y + 3 = -4x + 16

4x + y + 3 = 16

4x + y = 13

4 0

3 years ago

g Use this to find the equation of the tangent line to the parabola y = 2 x 2 − 7 x + 6 at the point ( 4 , 10 ) . The equation o

natali 33 [55]

Answer:

The tangent line to the given curve at the given point is $y=9x-26$ .

Step-by-step explanation:

To find the slope of the tangent line we to compute the derivative of $y=2x^2-7x+6$ and then evaluate it for $x=4$ .

$(y=2x^2-7x+6)'$ Differentiate the equation.

$(y)'=(2x^2-7x+6)'$ Differentiate both sides.

$y'=(2x^2)'-(7x)'+(6)'$ Sum/Difference rule applied: $(f(x)\pmg(x))'=f'(x)\pm g'(x)$

$y'=2(x^2)'-7(x)'+(6)'$ Constant multiple rule applied: $(cf)'=c(f)'$

$y'2(2x)-7(1)+(6)'$ Applied power rule: $(x^n)'=nx^{n-1}$

$y'=4x-7+0$ Simplifying and apply constant rule: $(c)'=0$

$y'=4x-7$ Simplify.

Evaluate y' for x=4:

$y'=4(4)-7$

$y'=16-7$

$y'=9$ is the slope of the tangent line.

Point slope form of a line is:

$y-y_1=m(x-x_1)$

where $m$ is the slope and $(x_1,y_1)$ is a point on the line.

Insert 9 for $m$ and (4,10) for $(x_1,y_1)$ :

$y-10=9(x-4)$

The intended form is $y=mx+b$ which means we are going need to distribute and solve for $y$ .

Distribute:

$y-10=9x-36$

Add 10 on both sides:

$y=9x-26$

The tangent line to the given curve at the given point is $y=9x-26$ .

------------Formal Definition of Derivative----------------

The following limit will give us the derivative of the function $f(x)=2x^2-7x+6$ at $x=4$ (the slope of the tangent line at $x=4$ ):

$\lim_{x \rightarrow 4}\frac{f(x)-f(4)}{x-4}$

$\lim_{x \rightarrow 4}\frac{2x^2-7x+6-10}{x-4}$ We are given f(4)=10.

$\lim_{x \rightarrow 4}\frac{2x^2-7x-4}{x-4}$

Let's see if we can factor the top so we can cancel a pair of common factors from top and bottom to get rid of the x-4 on bottom:

$2x^2-7x-4=(x-4)(2x+1)$

Let's check this with FOIL:

First: $x(2x)=2x^2$

Outer: $x(1)=x$

Inner: $(-4)(2x)=-8x$

Last: $-4(1)=-4$

---------------------------------Add!

$2x^2-7x-4$

So the numerator and the denominator do contain a common factor.

This means we have this so far in the simplifying of the above limit:

$\lim_{x \rightarrow 4}\frac{2x^2-7x-4}{x-4}$

$\lim_{x \rightarrow 4}\frac{(x-4)(2x+1)}{x-4}$

$\lim_{x \rightarrow 4}(2x+1)$

Now we get to replace x with 4 since we have no division by 0 to worry about:

2(4)+1=8+1=9.

6 0

3 years ago