Tuesday
February 21, 2017

Posts by Steve

Total # Posts: 48,695

Geometry and shape
Or, any regular n-gon with more than 4 sides and n an even number.
January 28, 2017

math
ar^3/ar^11 = 1/256 1/r^8 = 1/256 r = 2 Now you can find a, so the sum S8 = a(2^8-1)/(2-1) = 127a
January 28, 2017

math
r^2 = 2^2+9^2 = 85 so, if the unknown chord is 2x in length, 6^2+x^2 = r^2
January 28, 2017

Maths
If x is the son's age, 9x+15 = 3(x+15)
January 28, 2017

Math
#2 Huh? The planetary radius is equal to the separation? Do the planets touch, or is the separation between planetary surfaces? If so, then a cube with side 5r contains about 9 planets of radius r. So, the void ratio would be ((5r)^3 - 9*4/3 ?*r^3)/(9*4/3 ?*r^3) = (125-12?)/12...
January 28, 2017

Math
#1 You know that the weight is GMm/r^2 = 100 Replace M by 7M and r by 2r, and you have the new weight of G(7M)m/(2r)^2 = 7/4 GMm/r^2 = 175
January 28, 2017

Math
not quite sure what you're after, but d/dx (x^3) = 3x^2 d/dx (x^2+x) = 2x+1 If you want x where they are equal, then 3x^2 = 2x+1 3x^2-2x-1 = 0 (3x+1)(x-1) = 0 x = -1/3 or 1
January 28, 2017

Math
You have not asked a question. Clearly, to wrap all 80 boxes, you need 80 * 2 3/4 = 220 ft of ribbon. Now you have to decide just what it is you want to know...
January 28, 2017

Math
which region is shaded? Are the circles concentric? The area of the larger circle is 81?. The smaller circle has area 121?/4 = 30.25?
January 27, 2017

Math -
8x + 14y = 24 6x + 7y = 10 double the 2nd equation and you have 8x + 14y = 24 12x + 14y = 20 Now if you subtract the top from the bottom, the 14y cancels and you have 4x = -4 x = -1 Now use that in either original equation to find y: 8x+14y = 24 8(-1)+14y = 24 -8+14y = 24 14y...
January 27, 2017

Basic math
42.42
January 27, 2017

basic calculus
dA = 8?r dr dr = -1/2, so dA = 8?*200*(-1/2) = -800? m^2 so, the area is approximately 4?*200^2 - 800? = 159200?
January 27, 2017

Pre Cal
You know A, since A+B+C=180 a/sinA = b/sinB ...
January 27, 2017

Math
A\B is all x in A but not in B x not in A\B is all x in A&B or in B. So, A\(A\B) is all x in A and in (A&B or B) so, it is all x in A&B ? B
January 27, 2017

Math
The legs add up, but the eyes do not. You are correct that there are 19 animals. But then you go on to finish wrong. If there are m cows (moo) and c hens (cluck), 4m+2c = 52 2m+2c = 38 2m = 14 m = 7 7 cows and 12 chickens 7*4+12*2 = 28+24 = 52 legs 2*(7+12) = 2*19 = 38 eyes
January 27, 2017

Math
90 by 60
January 27, 2017

Math
Not sure how to parse your expression. B(A\B) is not correct syntax, since B is a set (A\B) is a set, call it C So, what does BC mean? Similarly, (A\B) is a set, so call it D. Again, what is DC? two set names juxtaposed has no meaning.
January 27, 2017

Algebra - units
Damon makes a good point. You know that you can always multiply by 1 without changing anything. If 6 meters = 1 minute, then 6m/1min = 1 1min/6m = 1 Those "conversion factors" are just different ways of writing 1! If you pick the correct expression, the unwanted ...
January 27, 2017

Maths
p+g+c = 100 100p+30g+5c = 1000 A little checking will show that he bought 94 chickens 1 goat 5 pigs
January 27, 2017

ALGEBRA MATRICES HELP
Turn to the section in your text. Start reading.
January 27, 2017

algebra
sounds good to me.
January 27, 2017

Math
well, four pounds more than three times the weight of his sister becomes 3w+4 so, now what do you think?
January 27, 2017

Math
well, each side is ?6.25 = 2.5 km, so since there are 4 sides, ...
January 27, 2017

Maths
see related question below
January 27, 2017

math
draw a diagram, including a diameter perpendicular to the chords. You will find a couple of 8-15-17 right triangles.
January 27, 2017

Precalculus
I think I can read this as z^7 = 1/?2 - 1/?2 i so, that means z^7 = cis 315° z = cis(315/7)° = cis45° + k*360/7 for k=1..6
January 27, 2017

Maths
If they work 3/2 as fast, it will take 2/3 the time.
January 27, 2017

algebra
clearly, when -16t^2 + 156t + 105 = 0
January 26, 2017

Math
h * h/2 * 1/2 = 100 h = 20
January 26, 2017

Math
well, 8 pts = 1 gal, so ...
January 26, 2017

math
42
January 26, 2017

trig
sin? = y/r cos? = x/r tan? = y/x tan? is the slope, so you have tan? = 5 r^2 = x^2+y^2 = 26
January 26, 2017

Math
it appears so.
January 26, 2017

Trig
csc^2 ? = 1+cot^2 ? so, ...
January 26, 2017

Algebra
a = 7 d = 3 Now you can answer the questions: T8 = a+7d Sn = n/2 (2*7 + (n-1)*3) > 425
January 26, 2017

formal language
ok. and ... ?
January 26, 2017

8th grade math
hmmm. I don' see no steenking triangles!
January 26, 2017

math
t = 2s k = t-3 t+s+k = 37
January 26, 2017

Math
so, we have (1,9) -> (3,-3) (3,12) -> (5,-6) (4,4) -> (6,2) x -> x+2 y -> 6-y = 3-(y-3) So, shift right 2 reflect across the line y=3.
January 26, 2017

Math
time = distance/speed, so time for sound to return: d/c time to fall: t = T-d/c d/c + gt^2/2 * d/t = T now just solve for d
January 26, 2017

algerbra
Looks like A to me. The prices are in the ratio 1:3:5:7, just like the times.
January 26, 2017

Math
450/(600+450+270) = 15/44
January 26, 2017

math
12^2 + L^2 = 20^2 L = 16 It's just a 3-4-5 triangle scaled up by a factor of 4.
January 25, 2017

Trigonometry
sin? = 1.2/4.4
January 25, 2017

Calculus
#1 correct ?[1,4] ?(1 + 1/4x) dx ?[1,2] ?(1+4y^2) dy where did you come up with [16,1]? The curve goes from (1,1) to (4,2) Note that ?(1+4y^2) is NOT (1 + 2y) ?(a^2+b^2) is not a+b !! #2. looks ok. For C, the radius is just x+2 For D, the radius is just 3-y
January 25, 2017

Math
use your standard conversion factors for gal/L and mi/km
January 25, 2017

Measurement
u = 10^-6 p = 10^-12 you surely have a list of prefixes - use them.
January 25, 2017

Algebra
you know that x = 3y-6 So, use that in the other equation: 20y + 35(3y-6) = 3795 20y + 105y - 210 = 3795 125y = 4005 y = 32.04 Now use that to find x. Odd, I expected an integer answer. Check for typos.
January 25, 2017

Algebra 1
just evaluate at x=5
January 25, 2017

Trigonometry with right triangles
you can always get a book on geometry and study it. I learned calculus on my own from my teacher's textbook. But I suggest you finish Algebra I before trying geometry or trig. It will give you a good foundation to work with.
January 25, 2017

Trigonometry with right triangles
what, you can't figure 90-25 ?
January 25, 2017

Trigonometry with right triangles
cos(x) = sin(90-x) That's what the co- in cosine means: sine of the complement.
January 25, 2017

Algebra 2
I get B. What did you do? Maybe we can figure what went wrong.
January 25, 2017

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

  1. Pages:
  2. <<Prev
  3. 1
  4. 2
  5. 3
  6. 4
  7. 5
  8. 6
  9. 7
  10. 8
  11. 9
  12. 10
  13. 11
  14. 12
  15. 13
  16. 14
  17. 15
  18. Next>>