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3 years ago

A sprinter can run 279 feet in 9 seconds. Find the sprinter's unit rate of feet per second.

Mathematics

1 answer:

Lorico [155]3 years ago

4 0

The answer is 31 feet per second :)

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Ples help me find slant assemtotes

FrozenT [24]

A polynomial asymptote is a function $p(x)$ such that

$\displaystyle\lim_{x\to\pm\infty}(f(x)-p(x))=0$

$(y+1)^2=4xy\implies y(x)=2x-1\pm2\sqrt{x^2-x}$

Since this equation defines a hyperbola, we expect the asymptotes to be lines of the form $p(x)=ax+b$ .

Ignore the negative root (we don't need it). If $y=2x-1+2\sqrt{x^2-x}$ , then we want to find constants $a,b$ such that

$\displaystyle\lim_{x\to\infty}(2x-1+2\sqrt{x^2-x}-ax-b)=0$

We have

$\sqrt{x^2-x}=\sqrt{x^2}\sqrt{1-\dfrac1x}$
$\sqrt{x^2-x}=|x|\sqrt{1-\dfrac1x}$
$\sqrt{x^2-x}=x\sqrt{1-\dfrac1x}$

since $x\to\infty$ forces us to have $x>0$ . And as $x\to\infty$ , the $\dfrac1x$ term is "negligible", so really $\sqrt{x^2-x}\approx x$ . We can then treat the limand like

$2x-1+2x-ax-b=(4-a)x-(b+1)$

which tells us that we would choose $a=4$ . You might be tempted to think $b=-1$ , but that won't be right, and that has to do with how we wrote off the "negligible" term. To find the actual value of $b$ , we have to solve for it in the following limit.

$\displaystyle\lim_{x\to\infty}(2x-1+2\sqrt{x^2-x}-4x-b)=0$

$\displaystyle\lim_{x\to\infty}(\sqrt{x^2-x}-x)=\frac{b+1}2$

We write

$(\sqrt{x^2-x}-x)\cdot\dfrac{\sqrt{x^2-x}+x}{\sqrt{x^2-x}+x}=\dfrac{(x^2-x)-x^2}{\sqrt{x^2-x}+x}=-\dfrac x{x\sqrt{1-\frac1x}+x}=-\dfrac1{\sqrt{1-\frac1x}+1}$

Now as $x\to\infty$ , we see this expression approaching $-\dfrac12$ , so that

$-\dfrac12=\dfrac{b+1}2\implies b=-2$

So one asymptote of the hyperbola is the line $y=4x-2$ .

The other asymptote is obtained similarly by examining the limit as $x\to-\infty$ .

$\displaystyle\lim_{x\to-\infty}(2x-1+2\sqrt{x^2-x}-ax-b)=0$

$\displaystyle\lim_{x\to-\infty}(2x-2x\sqrt{1-\frac1x}-ax-(b+1))=0$

Reduce the "negligible" term to get

$\displaystyle\lim_{x\to-\infty}(-ax-(b+1))=0$

Now we take $a=0$ , and again we're careful to not pick $b=-1$ .

$\displaystyle\lim_{x\to-\infty}(2x-1+2\sqrt{x^2-x}-b)=0$

$\displaystyle\lim_{x\to-\infty}(x+\sqrt{x^2-x})=\frac{b+1}2$

$(x+\sqrt{x^2-x})\cdot\dfrac{x-\sqrt{x^2-x}}{x-\sqrt{x^2-x}}=\dfrac{x^2-(x^2-x)}{x-\sqrt{x^2-x}}=\dfrac
 x{x-(-x)\sqrt{1-\frac1x}}=\dfrac1{1+\sqrt{1-\frac1x}}$

This time the limit is $\dfrac12$ , so

$\dfrac12=\dfrac{b+1}2\implies b=0$

which means the other asymptote is the line $y=0$ .

4 0

3 years ago

What's the missing side

Ann [662]

42 / 28 = 1.5

Therefore if we multiply 35 by 1.5 it would be:

52.5

7 0

1 year ago

You mow the lawn to earn your allowance. Each time you mow the lawn you earn $12 Write an equation for the number of dollars, d,

andrezito [222]

The equation is d=12m for amount you earn is 12 dollars per mow sesion.

12x10=120 after 10 times mowing you earned $120 (not bad)

8 0

3 years ago

What must be true of PQ?

yulyashka [42]

Interesting question
Usually when you look at something like that construction, you think that AB has been bisected by PQ and that the two segments are perpendicular. They are perpendicular but nowhere is that stated. So the answer is C because all the other answers are wrong.

PQ is congruent AB is not correct. As long as the arcs are equal and meet above and below AB there is no proof of congruency. In your mind widen the compass legs so that they are wider than AB and redraw the arcs. You get a larger PQ, but it has all the original properties of PQ except size.

PQ is not congruent to AQ. How would you prove conguency? You'd have to put both lines into triangles that can be proved congruent. It can't be done.

The two lines are not parallel. They are perpendicular. That can be proven. They meet at right angles to each other (also provable).

8 0

2 years ago

A boat is heading towards a lighthouse,

larisa86 [58]

Answer: 920.3 ft

Step-by-step explanation:

$\tan 7^{\circ}=\frac{113}{x} \\ \\ x(\tan 7^{\circ})=113 \\ \\ x=\frac{113}{\tan 7^{\circ}} \approx \boxed{920.3 \text{ ft}}$

4 0

1 year ago