Monday
April 27, 2015

Posts by Damon


Total # Posts: 20,993

Calculus
e^-2y dy = 2 x dx e-2y /-2 = x^2 + c e^-2y = -2 x^2 + c -2y = ln (-2 x^2+c) when x = 0, y = 1 -2 = ln(c) e^-2 = c -2 y = ln (-2x^2+e^-2) y = -(1/2) ln(-2x^2+1/e^2)
April 9, 2015

Math
2^2 - 3 = 1 4^2 - 3 = 13 7^2 - 3 = 46 etc :)
April 9, 2015

Calculus
d^2x/dt^2 = -22 dx/dt = 132 - 22 t x = Xo + 132 t - (1/2)(22) t^2 so x to stop from 132 ft/s 0 = 132 - 22 t t = 6 seconds to get dx/dt = 0 then x = 132 (6) - 11 (36) x = 792 - 396 = 396 ft to stop so 4 feet to spare Now I think you can handle Robin';s unfortunate experience.
April 9, 2015

science
I believe so. Think what is happening. gravity on big mass squeezing center of mass harder and harder
April 9, 2015

science
You are welcome.
April 9, 2015

science
Yes, A elliptical is old stars, little gas or dust to make new ones. C and D are exactly wrong :)
April 9, 2015

Calculus
r-b = 8 r+b = 20 solve for r and b find r/(r+b) r-b = 10 r+b = 30 solve for r and b find r/(r+b)
April 9, 2015

Math
y = 10 + x/3 y + x = 46 so y = 46 - x 46 - x = 10 + x/3 36 = 4 x/3 x = 27 y = 46-27 = 19 ======================== 25 q + 10 d = 1205 d = 59 - q so 25 q + 590 - 10 q = 1205 etc
April 9, 2015

science
yes, sometimes one moves behind the other, masking the pair look dimmer
April 9, 2015

math
You are welcome :)
April 9, 2015

math
I said (1/5) x + 2 = x - 4 multiply everything both sides by 5 x + 10 = 5 x - 20
April 9, 2015

math
I do not know. Do you mean y=(1/5)x+2 y=x-4 then x + 10 = 5 x - 20 x = 30/4 = 15/2 = 7.5 or do you mean y = 1/(5x) + 2 then 1 + 10 x = 5 x^2 - 20 x solve quadratic or do you mean 1/(5x+2) = x-4 1 = (5x+2)(x-4) 1 = 5 x^2 + 18 x - 8 etc
April 9, 2015

science
I believe so.
April 9, 2015

calc(steps and explanation also)
D^2 = x^2 + y^2 2 D dD/dt = 2 x dx/dt + 2 y dy/dt or dD/dt = (x dx/dt + y dy/dt)/D at t = 0 x = 0 y = 150 at t = 10 x = 580 y = 150+100 = 250 D = sqrt(580^2+250^2) = 631.6 dx/dt = 58 dy/dt = 10 so plug into dD/dt = (x dx/dt + y dy/dt)/D
April 9, 2015

math
12 x - 3 = 2 x + 4 10 x = 7 x = 7/10 y = 2(7/10) + 4 y = 14/10 + 4 y = 5.4
April 9, 2015

math
600 = 5 n + 10 d + 25 q n = 10 d + q = 25 600 = 50 + 10 d + 25 q or 550 = 10 d + 25 q or 110 = 2 d + 5 q so 2 d + 5 q = 110 2 d + 2 q = 50 ---------------- 3 q = 60 q = 20 you take it from there.
April 9, 2015

Calculus
angle a = tan^-1 (.5) da/dt = -.25 deg/min = -.009436 radians/min x = 25 = y tan a y = 25/tan a dy/dt = -25 sec^2 a da/dt /tan^2 a
April 9, 2015

physics
F = 2.51 (9.81) - 3.08 (9.81) sin 32.3 = 8.48 N a = F/m = 8.48/(2.51+3.08) 2.51(9.81) - T = 2.51 a
April 8, 2015

calculus
feet, yuuk :( oh well, g = 32 ft/s^2 in that case Vi = 42 sin 16 = 11.6 ft/s u = 42 cos 16 = 40.4 ft/s Horizontal problem: goes 20 ft at 40.4 ft/s t = 20/40.4 = .495 s Vertical problem with t = .495 s -m g = m d^2h/dt^2 d^2 h/dt^2 = -g = -32 dh/dt = Vi - 32.2 t h = Hi + Vi t...
April 8, 2015

math /fraction
HUH? (1/3)(12) = 4
April 8, 2015

calculus
draw a picture ! (a) 5*2 = 10 4 + 10 = 14 (b) 2 * 4 = 8 Unless I am missing something :)
April 8, 2015

calculus
v = (1/3) base area * height for anything pointy with straight sides slant height = R cut away sector angle a sector angle remaining = 2pi-a base radius remaining =r= 2piR(2pi-a)/2pi = R(2 pi-a) height h = sqrt(R^2-r^2) v = (1/3)(pi r^2)h plug and chug
April 8, 2015

Calculus (urgent help)
http://www.jiskha.com/display.cgi?id=1428548293
April 8, 2015

serious reply
29 *47 ------ ones * ones 7*9 = 63 ones * tens 7*20 =140 tens * ones 40*9 = 360 tens * tens 40*20 = 800 add = 1363
April 8, 2015

chemistry
Mercury sulfide Chemical Compound Mercury sulfide, mercuric sulfide, mercury sulphide, or mercury sulfide is a chemical compound composed of the chemical elements mercury and sulfur. It is represented by the chemical formula HgS. "******It is virtually insoluble in water...
April 8, 2015

Exponential Equations
It doubles ten times t x 0 1000 18 2000 one time 36 4000 2 times 54 8000 3 times 72 16000 4 times or 1000*2^4 90 108 ...... 180 1024*1000 = 1,024,000 = 1000*2^10
April 8, 2015

Math
24 % of 100 is 24 29 % of 100 is 29 She has 29 from Norway and 24 from France so 29 - 24 = 5
April 6, 2015

algebra
y = -2 x^3 + b x^2 + c x + d y(0) = 2 so d = 2 y = -2 x^3 + b x^2 + c x + 2 1 = -2 + b + c + 2 or b+c=1 -2 = 16 + 4 b - 2 c + 2 or -20 = 4 b - 2 c or -10 = 2 b - c 2 b - 1 c = -10 1 b + 1 c = 1 ---------------- 3 b = - 9 b = -3 etc
April 6, 2015

Physics
convert this into a projectile problem. First solve for velocity of projectile needed to reach ground at 10 meters when fired at 45 deg from height of 1 m Call that V1 Now find V2, the new velocity Q2 = .5 Q1 = .5 * V1 * A1 and Q2 = V2 A2 so V2 = .5 V1 (A1/A2) = .5*(1/.2) * V1...
April 6, 2015

physics
I have no idea. At constant speed propulsion force = drag force and mass is not part of the problem.
April 6, 2015

physics
gravity p = rho g h
April 6, 2015

physics
v = 2 - 10 t y = 2 t - 5 t^2 x = 1 t so t = x y = 2 x - 10 x^2
April 3, 2015

calculus
length = L width = w A = L w cost = 400 = 10(2L+2w) = 20(2w) 400 = 20 L + 60 w 20 = L + 3 w L = 20 - 2 w A = 20 w - 2 w^2 dA/dw = 0 = 20 - 4 w w = 5 L = 10
April 3, 2015

stastic
Given the following information about a sample, calculate a z score for a test grade of 91. = 87, s = 4.01 (Points
April 2, 2015

Algebra 2
http://www.easycalculation.com/statistics/standard-deviation.php
March 31, 2015

Algebra 2
https://www.easycalculation.com/statistics/standard-deviation.php add up the squares of the difference between each value and the mean divide it by 7 or 6 depending on if the population sd or just sd is desired take the square root.
March 31, 2015

physics
1 hp = 550 ft lbs/s so 25 hp = 13,750 ft lbs/s = Torque *radians/sec 1800 rev/m (2 pi rad/rev)(1 m/60 s) = 188 radians/s so Torque = 13750/188 = 72.9 ft lbs
March 31, 2015

science help.. pls help me dr.bob22 or damon
In one case it is ionic In the other case it is covalent However In both cases it is chemical
March 31, 2015

science help.. pls help me dr.bob22 or damon
Water is a covalent bond but a special polarized one called a "hydrogen bond" that results in attraction between water molecules
March 31, 2015

Algebra 2
If c is the hypotenuse (opposite the right angle) then c^2 = a^2 + b^2 or b^2 = 361 - 9 b = sqrt(352) = 18.8 sin A = a/c sin B = b/c
March 31, 2015

science help.. pls help me dr.bob22 or damon
I think so.
March 31, 2015

science help.. pls help me dr.bob22 or damon
I suspect that finding that electrons surround a nucleus would be fatal for the hypothesis of indivisibility :)
March 31, 2015

math - linear equation
y = x y = -x
March 31, 2015

science help.. pls help me dr.bob22
been there done that below metals and halogens are likely to form ionic bonds
March 31, 2015

pls help me dr.bob22 science
Yes Oscar it is B. but you mean Zn + 2HCl = H2 + ZnCl2
March 31, 2015

pls help me dr.bob22 science
Yes
March 31, 2015

pls help me dr.bob22 science
If it is an ionic bond it is an ion K+ will do as will F- Cl2 is a complete molecule Ne is a noble gas which is too proud to react much.
March 31, 2015

science help check
Metals from Group 1 are most likely to form ionic bonds Halogens, group 17, are also likely to form ionic bonds
March 31, 2015

Calculus - all the same question
If you can follow the one I did, you can do the rest.
March 30, 2015

Calculus
dC/dx = 100 - .2 x at x = 35 dC/dx = 100 - 7 = 93 dollars per club at a level of 35 clubs by the way total C for 35 clubs = 3877.5 or about an average of 111 dollars per club
March 30, 2015

Chemistry
one C per molecule? 6.02 * 10^23 molecules per mol 2.46 * 10^25 molecules *(1/6.02*10^23) = 40.9 mols How many grams? 40.9 * (12 + 4(35.5) ) what volume? grams / 2.71 g/mL
March 29, 2015

Differential Calculus
radius of circle = r side of square = s 10 = 4 s + 2 pi r so s = 2.5 - .5 pi r A = pi r^2 + s^2 or A = pi r^2 + 6.25 - 2.5 pi r + .25 pi^2 r^2 A = (.25 pi +1)pi r^2 -2.5 pi r + 6.25 I am going to use calculus, you can complete the square to find vertex of parabola dA/dr = 0 ...
March 29, 2015

Geometry
I used 400, use 500
March 29, 2015

Geometry
2 h + 2 w = 400 h + w = 200 w + 40 + w = 200 2 w = 160 w = 80 h = 120
March 29, 2015

Civics to Ms.Sue
Ms Sue is completely correct. There were presidents under the Articles.
March 27, 2015

Civics to Ms.Sue
It did not allow for a Department of Commerce :)
March 27, 2015

Civics to Ms.Sue
Well, the Articles of Confederation allowed for a president.
March 27, 2015

Algebra 1
0 = -0.04x^2+1.3x+56 or 0 = 0.04x^2 - 1.3x - 56 solve quadratic
March 27, 2015

us history
Now why would a state stay in the Union even if some of its residents had slaves? Maybe some of them did not have slaves and disagreed with the others?
March 27, 2015

us history
I do not think it is b or d
March 27, 2015

Algebra 1
.04 x^2 - 8.3 x - 4.3 = 0 http://www.webgraphing.com/quadraticequation_quadraticformula.jsp#
March 27, 2015

Algebra 1
y = x (-.04 x + 8.3) when is y = 0 at the start of course but also when .04 x = 8.3 or x = 207.5 meters I think you left a significant figure out :)
March 27, 2015

Algebra
y = k/x 300 = k /4 so k = 1200 y = 1200/150 y = 8
March 27, 2015

Algebra
I bet you mean [ f(x) - f(a) ] / (x-a) Parentheses are VITAL ! f(a) = -2 a^2 + 5 a - 1 so [ -2(x^2-a^2) +5(x-a) -1+1 ]/(x-a) = [-2(x-a)(x+a) + 5(x-a) ]/(x-a) = -2(x+a)+5 Note for future calculus purposes that the limit of this as a approaches a this becomes -4 x + 5
March 27, 2015

us history
I do physics actually. I just happened to know this.
March 27, 2015

us history
Jim Crow laws, C is right.
March 27, 2015

Algebra
distance = pi D in feet = pi * 64 * (1 mile/5280 ft) time = 25 s (1 h /3600 s) divide the distance in miles by the time in hours
March 27, 2015

algebra
y dy = x dx y^2/2 = x^2/2 + c or y^2 = x^2 + c (-3)^2 = 0 + c so c = 9 y^2 = x^2 + 9 y = +/- (x^2+9)^(1/2) since only y = -3 is given I think your answer correct
March 27, 2015

math
AB^2 = 64 + 4 = 68 BC^2 = 9 + 9 = 18 AC^2 = 25 + 25 = 50 Note that 68 = 50 + 18 therefore a right triangle
March 27, 2015

physics
F = m A F = (10.45)(2.5)
March 27, 2015

Economics
10 years 10.3 = 1.9 (1+r)^10 10 log(1+r) = log(5.42) log(1+r) = .0734 1+r = 1.184 so 18.4 percent per year
March 27, 2015

math
http://davidmlane.com/hyperstat/z_table.html
March 27, 2015

Pre-Calculus
Because she used parentheses.
March 26, 2015

Math
a) .15 * 15 = 2.25 NOT 1 c) correct e) corrtect
March 26, 2015

Math
b) CORRECT c) .045 * 1000 = 45 CORRECT ! d) NO way, you really feel 45 m is almost half a kilometer? e) 4500 / 1000 = 4.5 meters!
March 26, 2015

Math
old area = 400 ft^2 perimeter = 20+80 = 100 so 4 s = 100 s = 25 s^2 = area = 625 625 - 400 = ???
March 26, 2015

Math
4 = 1 + 3 or 2 + 2 or 3 + 1 so 3 out of 36 which is 1/12
March 26, 2015

Geometry
L w = 2 2 L * 3 w = 6*2 = 12
March 26, 2015

mathematical physics
we need the component of force in the direction of motion. F dot vector tangent to motion tangent to motion is velocity vector dX = Vdt if X is position vector and V is velocity vector X = t i + t j + t k V = dX/dt = i + j + k F dot V = y^2z^3 + 2 xyz^3 + 3x y^2 z^2 = t^5 + 2 ...
March 23, 2015

math
Thank you Reiny. Indeed we had quite a time getting ready for the first day of sailing practice.
March 23, 2015

math - binomial dist, no time to do it
use binomial distribution. I have to go clean seagull poop and snow off high school sailing floats, will check back this afternoon to see if you got it.
March 23, 2015

Algebra 1
y = x straight line through origin slope of one. y = 1 x + 0
March 22, 2015

CHEMISTRY
P V = n R T V same n same R same T same so partial pressure of each is 1/2 atm.
March 22, 2015

Algebra
http://www.jiskha.com/display.cgi?id=1427052839
March 22, 2015

Algebra
No problem :)
March 22, 2015

Algebra
I wrote (3 y - ) (y + ) and tried factors soon saw needed (3 y + ) (y - ) then fooled with 3 and 4 and then 6 and 2 until it worked
March 22, 2015

Algebra
Sure, fooled around with factors of 12 3 and 4 did not work, 1 and 12 did not work, so tried 6 and 2
March 22, 2015

Algebra
You are welcome.
March 22, 2015

Algebra
(3 y + 2)(y - 6)
March 22, 2015

math
combinations of 15 ten at a time n = 15 r = 10 C(n,r) = n!/[ r!(n-r)! ] = 15! /[ 10! (5!) ] = 15*14*13*12*11 /(5*4*3*2) = 15/15 * 14/2 * 13 * 12/4 * 11 = 7 * 13 * 3 * 11 = 3003
March 22, 2015

algebra
6 by 6 matrix of possibilities but 5 and 1 is the same as 1 and 5 for example so really not 36 possible results but only the diagonal and those below (or those above) so 6 + 5 + 4 + 3 + 2 + 1 = 21 possible combinations of which 3 add to 6 (they are (3,3)(2,4)(5,1) ) so THREE ...
March 22, 2015

College Math
new length = 36 - 2x new width = 24 - 2 x so V = (36-2x)(24-2x)x = 864x - 120 x^2 + 4 x^3 I am glad you do derivatives because I do not feel like finding the vertex. dV/dx = 864 -240 x + 12 x^2 0 = 72 - 20 x + x^2 x = [ 20 +/- sqrt(400 -288) ]/2 = [ 20 +/- 10.6 ] /2 = 15.3 or ...
March 20, 2015

physics
I can not because I do not know how far south the cat walked
March 17, 2015

physics
mg = 17*9.81 = 167 N weight 70 = mu (167) mu = 70/167 static 53 = mu (167) mu = 53/167 kinetic
March 17, 2015

Algebra
2 x^2 - 2 x - 2 = -y x^2 - x -1 = -(y/2) x^2 - x = -y/2 + 1 x^2 - x + 1/4 = -y/2 + 1 + 1/4 (x- 1/2)^2 = -(1/2) (y - 5/2) vertex at ( 1/2 , 5/2 ) if x = 6 y = - 2(36) + 12 + 2 = -58 =================== check (5.5)^2 =? -1/2 (-60.5) ??? 30.25 = 30.25 sure enough :)
March 17, 2015

math
2*60 + 2 w = 200 w + 60 = 100 w = 40
March 17, 2015

Math
1 % is .01 .02/5 is clearly less than .01 (it is .004) .2/5 is like .4/10 too big 2/5 even bigger 2/50 like 4/100 like .2/5 too big 2/500 is 4/1000 which is small enough (.004 again)
March 17, 2015

math
3/5 * 1/3 * x = 8 x = 8 * 15 / 3 x = 40 ================ check: 2/5 * 40 = 16 spent, 24 left 2/3 * 24 = 16 spent, 8 left --- sure enough
March 17, 2015

Vectors
vector QP = 3 i + 8 j + 2 k vector QR = 1 i + 6 j - 2 k cross product i j k 3 8 2 1 6 -2 -28 i + 8 j + 10 k or -14 i + 4 j + 5 k so for plane -14 x + 4 y + 5 z = d try (1,5,6) to get d -14 +20 + 30 = d d = 36 check with (-1,3,2) 14 + 12 + 10 = 36 sure enough we are on a roll ...
March 17, 2015

physics
(1/2) M V^2 = (1/2) K X^2 1330 v^2 = 4.12*10^6 (.0499)^2
March 17, 2015

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