Monday

February 27, 2017
Total # Posts: 48,842

**Calculus**

sin = y/r cos = x/r sinx = 1/5 cosx = -?24/5 = -2?6/5 cosy = 1/8 siny = ?63/8 = 3?7/8 I'll do sin(x+y) and you can apply the formulas for the rest. sin(x+y) = sinx cosy + cosx siny = (1/5)(1/8)+(-2?6/5)(3?7/8) = 1/40 - 6?42/40 = (1-6?42)/40 makes sense, since x+y is in QIII

*January 25, 2017*

**Algebra**

If the walkway has width w, then 2(6+2w + 10+2w) = 60.8

*January 25, 2017*

**maths**

a = 31 1/4 = 125/4 ar^(n-1) = 2 r^(n-1) = 8/125 Now, 8/125 = (2/5)^3 Looks to me like r = 2/5 and n=4 and the sequence is thus 125/4, 25/2, 5, 2 I think you'll find it adds up to 203/4

*January 25, 2017*

**Algebra**

Draw a diagram. Set the center of the ellipse at (0,0). Then we have semi-axes a = 74 b = 48 x^2/74^2 + y^2/48^2 = 1 Now plug in y=10 and find x. The distance d is then d^2 = x^2 + 10^2

*January 25, 2017*

**calculus**

3xy^3+4xy=63 3y^3 + 9xy^2 y' + 4y + 4xy' = 0 y'(9xy^2+4x) = -(3y^3+4y) y' = -(3y^3+4y)/(9xy^2+4x) So, at (9,1) y' = -7/117 Now you have a point and a slope, so the line is y-1 = -7/117 (x-9) Refer to http://www.wolframalpha.com/input/?i=plot+3xy%5E3%2B4xy%...

*January 25, 2017*

**Math 114**

so, did you check? 3+9=12 so, ok.

*January 25, 2017*

**MATH**

well, 4 for each kg, so ...

*January 25, 2017*

**math**

72/4 = 18 So, multiply all the lengths by 18 to get 54+72+36 = 162

*January 25, 2017*

**Math**

-8+3 = -5

*January 25, 2017*

**math**

1/5 boys absent means 4/5 present 4/5 boys = 160 = 4*40 So, there are 5*40 = 200 boys 2/5 of the students are boys 200 = 2/5 * 500 So, there are 500 students in all. Now you can see how many are girls.

*January 25, 2017*

**Trigonometry with right triangles**

Since <DEF is 60° and DE = ?2, EF=?6. So, the area is (?2*?6)/2 = ?3 Rather than all this *line in between answer D* stuff, you could have just written ?3/?2

*January 25, 2017*

**trigonometry**

If the pedestrian is x meters from the short building, 10/x = tan20°10' the distance to the tall building is 40-x You don't seem to care how tall the other building is, but if the tall building has height h, then (h-10)/40 = tan15°20'

*January 25, 2017*

**complex number help**

?-16 = ?(16 cis ?) = ?16 cis ?/4 = 2(1/?2 + 1/?2 i) = ?2 + ?2 i That is the 1st root. There is an equivalent root in each quadrant. See http://www.wolframalpha.com/input/?i=x%5E4+%3D+-16 Work the 5th root the same way, using de Moivre's theorem.

*January 25, 2017*

**maths**

assuming that the wood purchased will be used efficiently, the volume of wood is the outside volume less the inside volume. Since there are parallel sides, the inner dimensions are 5 cm less than the outer. Thus, the volume of wood is (200-5)(120-5)(75-5) = 1569750 cm^3 = 1....

*January 25, 2017*

**MATH**

x^2 * x^2 = (x*x)*(x*x) = x*x*x*x = x^4 or, x^2 * x^2 = x^(2+2) = x^4 or, x^2 * x^2 = (x^2)^2 = x^(2*2) = x^4

*January 25, 2017*

**Math**

f(5/2) is the remainder when f(x) is divided by (x - 5/2) This site can help: http://calc101.com/webMathematica/long-divide.jsp

*January 24, 2017*

**Math**

see http://calc101.com/webMathematica/long-divide.jsp

*January 24, 2017*

**Math**

well, (8-5)^2 = 3^2 = 9 I assume you can take it from there ...

*January 24, 2017*

**Calculus**

a little synthetic division will show that f(x) has roots in (-2,-1) and (0,1).

*January 24, 2017*

**Calculus**

F'(-4) = lim(h->0) [((-4+h)^3 + (-4+h)^2) - ((-4)^3+(-4)^2)]/h = lim(h->0) [(h^3-11h^2+40h-48)-(-48)]/h = lim(h->0) (h^3-11h^2+40h)/h = lim(h->0) (h^2-11h+40) = 40

*January 24, 2017*

**Calculus**

secx = 2 or -2 or, cosx = 1/2 or -1/2 One root in each quadrant.

*January 24, 2017*

**Calculus**

The slope of the line is (30000-280000)/10 = -25000 So, V(t) = 280,000 - 25,000t

*January 24, 2017*

**Math**

A - 1/2a = P

*January 24, 2017*

**Physics (9th)**

sorry. 26.39/4 = 6.59 don't know how I got so far off. So, fix t and redo the calculation...

*January 24, 2017*

**Physics (9th)**

recall that the equation for distance is s = vt + a/2 t^2 95 km/hr = 26.39 m/s So, it will take 26.39/4 = 6 seconds of braking to stop. s = 95*7 - 2*6^2 = 593 meters to stop I guess she had good eyes, seeing an antelope at half a km away! Or, maybe she just hit it, or swerved ...

*January 24, 2017*

**Algebra**

p = 3b-6 20b+35p = 3790 Now just solve for b and p to see how many of each there are.

*January 24, 2017*

**Math**

correct

*January 24, 2017*

**Math**

oops 47+30 = 77 > 70

*January 24, 2017*

**Math**

well, 70-47 = 23 so, any number bigger than 23 will make the statement true 47+30 = 73 > 70 I have no idea what outlandish method they taught to solve the problem.

*January 24, 2017*

**chem**

impatient much? see your other post...

*January 24, 2017*

**chem**

29 moles of O2 --> 58 moles of H2O So, how many grams is that?

*January 24, 2017*

**find the equation**

review the point-slope form.

*January 24, 2017*

**Standard Form**

slope=0 so, the line is of the form y=k for some k.

*January 24, 2017*

**trig**

forget you algebra I?? subtract 2 from both sides ...

*January 24, 2017*

**math**

initial amount of $57 expense = 57 materials cost $7 for each necklace expense = 57 + 7x sales = 26x ...

*January 24, 2017*

**math geometry**

This might help. google can provide more help.

*January 24, 2017*

**maths - Typo?**

a = ar^3 + 13.5 ar^3 = ar^2 + 9 a(1-r^3) = 13.5 ar^2(r-1) = 9 Now divide both sides to get (1-r^3)/(r^3-r^2) = 13.5/9 2-2r^3 = 3r^3-3r^2 5r^3-3r^2-2 = 0 Hmmm. No real solutions.

*January 24, 2017*

**Algebra**

No, the solutions are the values of x which make x = 0 x+5 = 0 x+2 = 0 x = 0, -5, -2 x = 0 5x-1 = 0 x+4 = 0 x = 0, 1/5, -4

*January 24, 2017*

**Calculus**

Your pieces overlap. That is not the way to define a piecewise function. Looks like your inverse function will also be piecewise, no? Just take the inverse on each piece.

*January 24, 2017*

**Anonyms**

c = 2?r = 4? so, r=2 a = ?r^2 = 4? A square with area 4? has side ?(4?) = 2?? So, its perimeter is 4*2?? = 8?? Note that 8?? > 4?. A circle has minimum perimeter for a given area. Or, a circle has maximum area for a given perimeter.

*January 24, 2017*

**math**

Odd that you know it's a Bernoulli equation, yet seem to have no technique for solving such a well-known form. y = ±1/?(cx^2-6x^3) If you have not studied them, try here: http://tutorial.math.lamar.edu/Classes/DE/Bernoulli.aspx

*January 24, 2017*

**Math geometry**

x = 20+3(180-x)

*January 24, 2017*

**Trig**

you're welcome.

*January 24, 2017*

**math**

)&( ? !

*January 24, 2017*

**Math - Algebra 1**

16 cows * 4.5 cups/cow/day * 7days * 1bucket/250cups * $26.75/bucket = $53.93

*January 24, 2017*

**Math - Algebra 1**

for a given perimeter, a square has the largest area.

*January 24, 2017*

**math**

a square with diagonal d has side length s = d/?2 And the question should have been worded: The walkway is 24 meters long. To the nearest tenth of a meter, how long is the side of the playground?

*January 24, 2017*

**Geometry probability**

There are 5 blue out of 12 marbles. So, there is a 5/12 chance of drawing a blue marble. That means that in 4 draws, the chance of drawing a blue on the 1st draw only is 5/12 * 7/11 * 6/10 * 5/9 = 35/396 Now, add that to the chance of drawing a blue only on the 2nd, 3rd, of ...

*January 24, 2017*

**Trig**

3 - 1/5 tanx = 16/5 -1/5 tanx = 1/5 tanx = -1 Now recall that tanx is negative in QII and QIV

*January 24, 2017*

**Maths**

well, one revolution is ?d = 14? cm, so ...

*January 24, 2017*

**help with trigonometry??**

draw a diagram. review your basic trig functions. It should be clear that if the height is h, h/112 = tan62°

*January 24, 2017*

**math**

?2.8x+5.6 < 8.4 -2.8x < 2.8 x > -1

*January 24, 2017*

**algebre**

using the law of cosines, 12^2 = 10^2 + 8^2 + 2*10*8 cos? = 164+160cos? BD^2 = 10^2 + 8^2 - 2*8*10 cos? = 164 - 160(-20/160) = 184 BD = 13.56

*January 24, 2017*

**Math grade 6, ratio**

a = 3/7 b = 2/3 a = 2/3 * 3/7 = 2/7 c = 1 - 3/7 - 2/7 = 2/7 b/c = (2/7) / (2/7) = 1 c = 2/3 a = a-49 1/3 a = 49 a = 147 c = 2/3 a = 98

*January 24, 2017*

**Grade 6, ratio**

if there were x 50-cent coins and y dollar coins, then if 6 dollars were replaced with 12 halves, x/y = 3/4 (x-6)/(y+12) = 1/3 clearing the fractions, we have 4x = 3y 3(x-6) = y+12 4x-3y = 0 3x-y = 30 now we see that y=3x-30, so 4x-3(3x-30) = 0 4x-9x+90 = 0 5x = 90 x = 18 So, ...

*January 24, 2017*

**Math**

that is correct.

*January 24, 2017*

**Math**

they add to 90 degrees, so 4x+5x = 90 find x, and then the angles are 4x and 5x

*January 24, 2017*

**Algebra**

1 3/5 and 2 1/2 are both bigger than 1. how can each person eat more than the whole pizza? In any case, 1 3/5 + 2 1/2 = 1 6/10 + 2 5/10 = 3 11/10 = 4 1/10

*January 24, 2017*

**Math**

This just the sum of the first 12 terms of a geometric sequence with a = 3600 r = 1.01 So, 3600 * (1.01^12 - 1)/(1.01-1) = 45,657 Not quite sure how to get your answer.

*January 24, 2017*

**Algebra**

you know that x^a * x^b = x^(a+b) x^(1/2) * x^(1/2) = x^(1/2 + 1/2) = x^1 = x ?x * ?x = x (?x)^2 = (x^(1/2))^2 = x^(2 * 1/2) = x^1 = x

*January 24, 2017*

**Math**

they are equal due to the associative property of multiplication: (a*b)*c = a*(b*c)

*January 24, 2017*

**Calc 2**

Hmmm. Kind of murky. In any case, it's just the chain and product rules. y = ?x e^(x^2) (x^2+1)^10 Recall that if y=uvw then y' = u'vw + uv'w + uvw' So, that would give us y' = 1/(2?x) * e^(x^2) * (x^2+1)^10 + ?x * 2x e^x^2 * (x^2+1)^10 + ?x * e^x^2 * ...

*January 24, 2017*

**Math**

correct. It is shown.

*January 23, 2017*

**Math**

if you mean that the 2nd was sold for 20% more than the first, then if the first sold for x, we have x + 1.2x = 3000 If not, then I'm not sure what each gaining 20% on the other means...

*January 23, 2017*

**Algebra**

half as many workers, so twice as long.

*January 23, 2017*

**Math**

215lb * 1kg/2.2lb = 97.727kg 97.727kg * (4.8mg/day)/kg = 445.091 mg/day 445.091 mg/day * 11ml/16mg = 306ml/24hr = 76.5 ml/(6hr)

*January 23, 2017*

**math**

square roots that end with a decimal?? square roots are called radicals, but so are cube roots, etc. 3?2 = ?18 = ?18.000 not sure where you're going with this.

*January 23, 2017*

**Precalulus**

I am assuming the usual carelessness with parentheses, and getting -2/(-3x-7) - 3/(2x-1) = 3/2 -2*2(2x-1) - 3*2(-3x-7) = 3(-3x-7)(2x-1) 4-8x + 18x+42 = -18x^2-33x+21 18x^2+43x+25 = 0 (x+1)(18x+25) = 0 x = -1 or -25/18 Assuming a little less sloppiness, I'd read (-2/-3)x - ...

*January 23, 2017*

**11th Grade Algebra 2**

just review the techniques of long division. You can see all the details if you play around here: http://calc101.com/webMathematica/long-divide.jsp It's just like regular numeric long division, as long as you line up the powers of x the way you do columns of digits in big ...

*January 23, 2017*

**Math**

you can play around with these things here, and see all the details. http://calc101.com/webMathematica/long-divide.jsp

*January 23, 2017*

**Math**

96/6 = 16 All we know is that the base has an area of 16 ft^2. I'm sure you can some up with two factors of 16 which could be the length and width.

*January 23, 2017*

**MATH @Damon @ms. Sue**

f(x) = 2*3^x on [0,1] the average rate is (f(1)-f(0)))/(1-0) = (2*3^1 - 2*3^0)/1 = 6-2 = 4 on [2,3] the average rate is (f(3)-f(2))/(3-2) = (2*3^3 - 2*3^2)/1 = 54-18 = 36 the ratio of the rates is 36/4 = 9. The reason the rate increases is that exponentials grow ever faster. ...

*January 23, 2017*

**Science**

is it a windy day? is it raining? is the street sloping? curving?

*January 23, 2017*

**Math**

12:01 12:29 12:46 I'm sure you can come up with others. Heck, use a clock if you need to.

*January 23, 2017*

**Calculus**

#1. Using horizontal shells of thickness dy, r = y h = y^2 - (3y^2-2) = 2-2y^2 v = ?[0,1] 2?rh dy = 2??[0,1] y(2-2y^2) dy = ? You got r and h reversed, but the product was luckily the same. Unfortunately, you added instead of subtracting. Using discs of radius y and thickness ...

*January 23, 2017*

**Math**

well, 9 is 3/4 dozen, so it will cost 3/4 of 20, or 15 Or, since the unit cost as the ratio of money:bananas is constant, x/9 = 20/12

*January 23, 2017*

**HELP PLEASE**

the C balances as written, since there is one on each side. That leaves you with CH4 + ?O2 > CO2 + ?H2O you have 4H on the left, so you will need 2H2O on the right. That gives CH4 + ?O2 > CO2 + 2H2O That balances the C and H, so now you need 4O on the left, which is 2O2 ...

*January 23, 2017*

**Math**

correct, so now you can find the breadth, b.

*January 23, 2017*

**Math**

2(b + 2b-8) = 56

*January 23, 2017*

**algebra**

an equation has no coordinates. If you want the coordinates of the two lines' intersection, then just solve for x and y. The first equation tells you that y = 2x+11 so use that in the 2nd equation and you have x+4(2x+11) = 17 x+8x+44 = 17 9x = -27 x = -3 Now, y = 2x+11 = 2...

*January 23, 2017*

**algebra**

sorry. (a) we don't have the test in question (or even the class!) (b) we don't help students cheat we will help you learn how to solve the problems, though, if it's not already too late ...

*January 23, 2017*

**Math**

If those are logs to the same base, then 5(x-2)*8(x-4) = 6(x-1) x = (123+?2089)/40 If those are logs to different bases (5,8,6), it takes some more work. Changing all to natural logs, we have Log5(x-2) + log8(x-4)= log6(x-1) ln(x-2)/ln5 + ln(x-4)/ln8 = ln(x-1)/ln6 ln8*ln6*ln(x...

*January 23, 2017*

**Pre-Calculus**

the water surface has a constant area of 800 in^2. So, every inch of water adds a volume of 800 in^3. So, after t minutes, the tank holds v(t) = 7*800 + 800t in^3 You should probably restrict the domain of t so that the tank does not overflow.

*January 23, 2017*

**Study School (Math)**

t+u = 9 10t+u+9 = 10u+t Now just find t and u, then answer the question.

*January 23, 2017*

**college algebra**

try writing it without the words. This is a math problem, not an English essay ... -4/(2x+3) + 1/(x-1) = 1/((2x+3)(x-1)) -4(x-1) + 1(2x+3) = 1 -4x+4 + 2x+3 = 1 -2x+7 = 1 2x = 6 x = 3

*January 23, 2017*

**college algebra**

Put the words into math. You are told that: s+g = 10000 g = s-3000 Now just solve for s and g.

*January 23, 2017*

**Math**

(48ft*48ft) * (1can/192ft^2) = (2304ft^2) * (1can/192ft^2) = 12 cans

*January 23, 2017*

**maths**

This one is long, but not overly complicated. I expect that u=x^2 is a good substitution to start with. Then I expect a trig or hyperbolic trig substitution will come in handy. I suggest you enter your integrand at this URL and it will show all the steps involved. http://www....

*January 23, 2017*

**Math**

no, since the discriminant (b^2-4ac) is negative. The roots are complex.

*January 22, 2017*

**math question**

distance=speed*time So, if it flew at 800km/hr for x hours, then it flew at some unknown speed s for 2x hours: 800x + s*2x = 700*3x 800+2s = 2100 2s = 1300 s = 650

*January 22, 2017*

**Precalculus**

oops. the cubes factor as (x + (x+1))(x^2-x(x+1)+(x+1)^2)

*January 22, 2017*

**Precalculus**

For the complex solutions, note that you want x^6 - (x+1)^6 = 0 This is just the difference of two squares, so it factors as (x^3 - (x+1)^3)(x^3 + (x+1)^3) = 0 The left factor becomes just a simple quadratic when expanded, as the x^3 terms go away. The right factor is the sum ...

*January 22, 2017*

**Algebra2**

f(x)=3x-7 and g(x) = -2x-6 find (fog)(4)

*January 21, 2017*

**Algebra2**

let f(x) = -2x+4 and g(x) = -6x-7 find f(x)-g(x)

*January 21, 2017*

**Math**

w = 4m m + w = 150

*January 18, 2017*

**math**

assuming the cost is 63/m^2, it will come to (5-2*.5)(4-2*.5)(63)

*January 18, 2017*

**science - eh?**

huh? If it keeps accelerating, will it come to rest at all? I cannot parse the language to come up with a question.

*January 18, 2017*

**math**

the height:shadow ratio is the same, so x/42 = 6/7

*January 18, 2017*

**math**

1/5 = 0.2 = 20% think you can handle that now?

*January 18, 2017*

**Math**

Nope. y2 = -5, not 5 (-5-3)/(1 - -3) = -8/4 = -2

*January 18, 2017*