Monday

February 8, 2016
Total # Posts: 37,488

**math**

floor: 12*10 long walls: 2(12*8) short walls: 2(10*8) Now add 'em up.
*February 8, 2016*

**Math**

29.95/1.02 = ?
*February 8, 2016*

**physics**

see related questions below
*February 8, 2016*

**Math**

1B Can you not tell that by looking at the figure? 2B a square is a rectangle with 4 equal sides. 3B just look at the letters, keeping them in the same order.
*February 8, 2016*

**Math**

apparently her notation is ^. for * meaning multiply. Trés strange.
*February 8, 2016*

**math**

First, that's pi not pie!!! Just start subtracting 2pi from your angle until the result is between 0 and 2pi. 3pi - 2pi = pi we have a winner!
*February 8, 2016*

**maths**

When asking how much one value is than another, you just subtract. If I ask How much bigger 10 is than 3, you do 10-3=7. So, (-39)-(-98) = -39+98 = 59
*February 8, 2016*

**math**

well, did you try actually verifying it? (5/8)(-3/5) + (1/16)(-3/5) = -15/40 - 3/80 = -33/80 3/16 - 3/5 = 15/80 - 48/80 = -33/80 I guess your answer is correct.
*February 8, 2016*

**Math**

If there are x lbs, each one gets x/3 so x >= 10.5 x/3 >= 3.5
*February 8, 2016*

**Algebra**

105 mi/hr = 154 ft/s So, it takes 60.5/154 seconds
*February 8, 2016*

**Math**

the independent variable is the one which you can set to whatever you want: in this case, the number of students. Since there is a fixed cost for each student, the cost depends on the number of students.
*February 8, 2016*

**MATH**

5x + 4.20(26-x) = 4.80*26
*February 8, 2016*

**MATH**

stop posting problems which refer to a pictures we cannot see.
*February 8, 2016*

**math**

3^x * 5^x + 1=20 (3*5)^x = 19 15^x = 19 x = log1519
*February 8, 2016*

**Math**

hard to say, with no picture to see.
*February 8, 2016*

**Math**

area grows as the square of the sides. So, the areas are in the ratio (2/3)^2 = 4/9
*February 8, 2016*

**Math**

If you mean of a circle, it is that portion of a circle subtended by a central angle. That is, if two radii are drawn, the sector is the area between them.
*February 8, 2016*

**Maths**

(22^3 * 7/8)/(π/6 * .5^3) ≈ 142,353
*February 8, 2016*

**math**

p(w) = 7+2w
*February 8, 2016*

**Calculus (double integral) PLEASE HELP!**

This exact transformation is discussed on pp 3-5 of http://math.etsu.edu/multicalc/prealpha/Chap4/Chap4-4/printversion.pdf
*February 8, 2016*

**Math**

p(t) = 157354 * 2^t
*February 8, 2016*

**math**

One way is elimination, where you multiply the equations to enable addition to eliminate one variable: 6x+4y = -36 -6x+15y = -78 now if you add them up you get 19y = -114 Thus, having y, you can now get x from either equation.
*February 8, 2016*

**math**

the area of the border is (500)(130)-(500-2*25)(130-2*25) = 29000 cm^2 Now you can find the cost
*February 8, 2016*

**trigonometry**

Remember the Pythagorean Theorem? The distance d is d^2 = 200^2 + 60^2
*February 7, 2016*

**Calculus (Jacobian question)**

This type of problem is discussed on pages 3-5 at http://math.etsu.edu/multicalc/prealpha/Chap4/Chap4-4/printversion.pdf
*February 7, 2016*

**Math**

mass of pure gold would be 5*18*4 cm^3 * 19.3 g/cm^3 = 6948g so, what do you think?
*February 7, 2016*

**calculus**

∫ x^3/√(3x^2-5) dx x = √(5/3) secθ 3x^2-5 = 5tan^2θ dx = √(5/3) secθ tanθ dθ and the integral becomes ∫ √(5/3)^3 sec^3θ/(√5 tanθ) √(5/3) secθ tanθ dθ = 5/9 √5 ∫sec^4&#...
*February 7, 2016*

**physics**

oops. the horizontal speed is 33.437 cos20° make that fix...
*February 7, 2016*

**physics**

h(t) = vt - 1/2 g t^2 3.5v - 4.9*3.5^2 = -20 v = 11.436 That v is the vertical speed at takeoff. So, the entire initial speed is 11.436/sin20° = 33.437 Use that speed and d = vt to get the horizontal distance traveled. d = 33.437 * 3.5 = 117.028
*February 7, 2016*

**Precalculus**

Huh? Forget your Algebra I? Anyway, just type in your function at wolframalpha.com
*February 7, 2016*

**Trigonometry**

Draw a diagram, and you will see that x cot14° + x cot18° = 55 x = 55/(cot14° + cot18°)
*February 7, 2016*

**math**

.42
*February 7, 2016*

**Algebra**

u = kp^3/d
*February 7, 2016*

**Algebra**

add up the value of the parts: 8.40x + 14.70(70-x) = 14.61*70 Expect a value of nearly zero for x, since the price of the mix is very close to the price of the Mexican coffee.
*February 7, 2016*

**Calculus**

The paraboloids intersect along an ellipse 3x^2+2y^2 = 6 So, the volume is (using symmetry) v = 4∫[0,√2] ∫[0,√((6-3x^2)/2)] (6-x^2-y^2)-(2x^2+y^2) dy dx = 3π√6
*February 7, 2016*

**math**

you are right
*February 7, 2016*

**Math**

You are correct.
*February 7, 2016*

**Numericals**

v = √2as = √(2*9.8*15) = 17.146 m/s Since the ball's energy PE = mgh, if it loses 40% of its energy, it will lose 40% of its height, so it will bounce to 9 m. Or, since PE becomes KE just before impact, KE = 1/2 mv^2 The rebound velocity will be .6 * 1/2 m*17....
*February 7, 2016*

**calculus**

see related questions below.
*February 7, 2016*

**radicals**

just multiply roots like anything else. If a square root contains a perfect square, like 16 or 49, you can factor the 4 or 7 out of the root. For this problem, √8(√(9ab)/√(3b) + √(27a)) 2√2 (√(9ab/3b) + 3√(3a)) 2√2 (√(3a...
*February 7, 2016*

**calculus**

a = (90-30)/10 = 6 km/hr-s s = 1/2 at^2 = 3 km/hr-s * (10s)^2 = 300 km-s/hr = 300 km-s/hr * 1hr/3600s = 300/3600 km = 1/12 km or, since you want to use calculus, a = 6km/hr-s = 6km/hr-s * 1hr/3600s = 1/600 km/s^2 so, a(t) = 1/600 v(t) = 1/600 t s(t) = 1/1200 t^2 s(10) = 100/...
*February 7, 2016*

**math**

if compound interest, 400(1+r)^4 = 480 (1+r)^4 = 1.2 r = .0466 Is your new r (r + .02)=.0666 or is it 9*1.02 = .0475 ?? Do a similar calculation if simple interest.
*February 7, 2016*

**Math**

f(x) = √(x-2) You know that the domain of √x is x>=0. So, you need x-2 >= 0 Not too hard, eh?
*February 6, 2016*

**maths**

well, sin(x) = 125/250 = 1/2 look familiar?
*February 6, 2016*

**Maths**

If you draw a careful diagram, you will see that the altitude is 240cm between the bases. Using similar triangles, you can see that if the pyramid were not chopped off, its height would be 320/3. So, the missing part is a pyramid of base side 80 and height 400/3. Now just work...
*February 6, 2016*

**Linear Algebra**

First, be sure you understand a matrix null space. Google is your friend. Te null space is all vectors x such that xA = 0 I'm having a hard time understanding A[1, 1, 1]^t = [2, 3]^t = A[2, 3, 4]^t How can they all be equal?
*February 6, 2016*

**Calculus**

Just integrate a = ∫[-1,0] (13-5x)/3 - (-6x) dx + ∫[0,2] (13-5x)/3 - x/2 dx = 13/6 + 13/3 = 13/2 Or The distance from (0,0) to (1,2) is √5. Let that be the base of the triangle. The altitude is the distance from (-1,6) to y=x/2 (or -x+2y+0=0) is |1+12|/√...
*February 6, 2016*

**Physics 30**

see Coulomb's law.
*February 6, 2016*

**Physics 30**

since only one current is given, I'll assume the R are in series E = IR, so 22 = .012(27+R)
*February 6, 2016*

**Physics 30**

come on, that's ohm, not omega. Omega is just the symbol used for the unit. 1A = 1C/s P = I^2R = (10/5)^2 * 25 = 100 W energy = power * time
*February 6, 2016*

**Physics 30**

since the force is inversely proportional to d^2, it will be reduced by a factor of 25.
*February 6, 2016*

**PHYSICS**

Coulomb's law is discussed here: http://www.physicsclassroom.com/Class/estatics/U8L3b.cfm just plug in your numbers.
*February 6, 2016*

**physics & math**

well, recall that v = √(2as) so, plug in your a and s.
*February 6, 2016*

**Calculus (polar coordinates)**

recall that dA = r dr dθ so, since x = r cosθ you have ∫[0,π/2] r cosθ r dr dθ = ∫[0,π/2] r^2 cosθ dr dθ But, r changes at π/4, so that gives ∫[0,π/4]∫[0,2sinθ] r^2 cosθ dr dθ + ∫[&#...
*February 6, 2016*

**Math**

Hmm. I'm still unclear. What is an example where switching the hands is invalid?
*February 6, 2016*

**Math**

Do you mean the physical clock hands are switched? No problem. I mean, the hands still point to places on the dial, right? If you mean the digital time has hh:mm swapped to mm:hh, then any time from 01:01 to 01:12 is ok and so on for the other hours. As long as the minutes are...
*February 6, 2016*

**Math**

<head slap> dontcha hate it when that happens? Still, the aha! moment is worth the pain.
*February 6, 2016*

**Math**

recall that the y-intercept is where the line crosses the y-axis. The line y=16 clearly crosses the y-axis at y=16, because it is 16 for any value of x, in particular, x=0.
*February 6, 2016*

**calculus**

The curves intersect at (0,0) and (3,9) So, rotating around the x-axis, using discs: v = ∫[0,3] π(R^2-r^2) dx where R=3x and r=x^2 v = ∫[0,3] π((3x)^2-(x^2)^2) dx = 162π/5 shells (tubes): v = ∫[0,3] 2πrh dy where r=y and h=(√y)-(y/3...
*February 6, 2016*

**Physics**

A: since the initial v=0, only g is acting on the mass. B: ok C: D = bv^2 = b(√(mg/b)/2)^2 = mg/4 SO, net a = mg/4 - mg = -3/4 mg
*February 6, 2016*

**Pre-Calculus**

looks good to me. You can always check your answer by typing in the polynomial at wolframalpha.com
*February 6, 2016*

**Pre-Calculus**

enter your coefficients at http://www.mathportal.org/calculators/polynomials-solvers/synthetic-division-calculator.php Looks like you goofed somewhere.
*February 6, 2016*

**Do I have time**

no, but google shows many hits, the first at (wow!) biography.com
*February 6, 2016*

**Do I have time**

Sure you have time. 3 days for 4 more paragraphs? No sweat, if you get to work. Of course, judging by your posting, you have some serious proofreading to do ...
*February 6, 2016*

**algebra 2**

the domain for all polynomials is (-∞,∞) Think about it -- pick any value of x and you can calculate f(x).
*February 6, 2016*

**algebra**

At first I thought your work was a hodgepodge, but further study shows that you are correct. except that 95/7 is not 13. Should have been 91, so you messed up somewhere.
*February 6, 2016*

**Calculus**

No, at 20 mi/hr, every mi/hr increase in speed decreases the fuel consumption by .05 gal/hr. Keep track of the units. Seems kind of odd though, that rate of fuel consumption decreases with increasing speed...
*February 6, 2016*

**Calculus**

#1 ok #2 f' = dc/dv = (gal/hr)/(mi/hr) = gal/mile #3 sort of - see units for #2.
*February 6, 2016*

**Math Radicals**

just expand like normal binomial multiplication: (a+b)^2 (2√5+3)(2√5+3) = (2√5)^2 + 2(2√5)(3) + 3^2 = 4*5 + 12√5 + 9 = 20 + 12√5 + 9
*February 6, 2016*

**math**

p(t) = 4i+8j + (4i+j)t q(t) = 4i+3j + (2i+5j)t the distance pq is d(t) = p(t)-q(t) = 5j + (2i-4j)t = (2t)i + (5-4t)j |d| = √((2t)^2 + (5-4t)^2) = √(20t^2-40t+25) Hmmm. I get √5 as the minimum distance. Better check my math.
*February 6, 2016*

**Mathematics**

8x^3 = 0
*February 6, 2016*

**Math and Physic**

Right off, I'd say the building has zero velocity. as for time to fall, h - 4.9t^2 = 0 plug in t= 7.57
*February 6, 2016*

**Calculus**

If the width is x and the rectangle's height is y, then x+2y + π/2 x = 24 so, y = (24-(1+π/2)x)/2 The area is a = xy + π/2 (x/2)^2 = x(24-(1+π/2)x)/2 + π/8 x^2 = 12x - (1/2 + π/8)x^2 Now just set da/dx=0 to find where the max occurs. Or, use ...
*February 6, 2016*

**sinusoidal functions**

The central axis is at y = 5 y = sin(x)+5 Two consecutive minima are found at (3, −1) and (13, −1) So, the period is 10, the amplitude is 5+1=6, and the shift is 3. cos has max at x=0, but we have a minimum, so y = -6cos(π/5 (x-3))+5 see the graph at http://...
*February 6, 2016*

**math**

rear legs get 2/3 and front get 1/3 now divide those amounts by 2, since there are two front and two rear legs.
*February 6, 2016*

**calc**

f'(p) is the rate of change of quantity as price changes Think of the units: f is yards p is dollars, so df/dp = yards/dollar no idea whether f'(16) is positive or negative. However, it is likely that as price goes up, demand goes down.
*February 6, 2016*

**system of equations**

a + 30b = 1300 a + 80b = 2200
*February 5, 2016*

**Calculus**

looks ok to me y = f^3(g(x)) dy/dx = 3f^2 df/dg * dg/dx for example, y = sin^3(x^2+1) dy/dx = 3sin^2(x^2+1) cos(x^2+1) (2x)
*February 5, 2016*

**Linear Algebra**

depends. what is b? As long as the matrix has a nonzero determinant, there will be a solution.
*February 5, 2016*

**Math**

Looks more like A to me.
*February 5, 2016*

**Geometry**

google online drawing tools. Or, hey! How about this idea? Go Buy Some Graph Paper! Actually, there are online sites which have graph paper you can print.
*February 5, 2016*

**Maths**

review the cotangent function. Draw a diagram and you will see that the distance the plane has flown is 880 cot24°30' - 880 cot67°40'
*February 5, 2016*

**math**

2a+3c = 44.40 3a+6c = 78.00 That's the same as 2a+3c = 44.40 a+2c = 26.00 subtract and you get a+c = 18.40 Note that we don't actually have to find the price of the individual tickets.
*February 5, 2016*

**Geometry**

#1 ok. #2 you figured the length of the hypotenuse. The perimeter is 9+12+15 = 36.
*February 5, 2016*

**math college readiness**

h(t) = 105 - 9t - 16t^2 When does it hit the ground? That would be when h(t) = 0, right? So, just solve the quadratic equation.
*February 5, 2016*

**Math**

If they are linear equations, it is A. Parallel lines (same slope) never intersect. But lines with different slopes must intersect somewhere.
*February 5, 2016*

**Math**

you are correct.
*February 5, 2016*

**math**

If the unknown force is x, then you just need to solve 550 - 300 + x = 0 because the sum of all the forces needs to be zero. I think that once you get your answer you will (a) see why the given formula works (b) notice the typo as written
*February 5, 2016*

**math (sequence and series )**

salary: 1st 8 years: 240 years >= 9: Tn = 9500+360(n-8) Total after 8 years: 8*240 = 1920 n years: (n > 8) Sn = (n-8)/2 (2*9500 + (n-9)*360) So, plug in your numbers for n
*February 5, 2016*

**Physics**

if the graph shows the actual error, just divide that by the correct value. For example if the correct value is 20, and the error is 3, then the percent error is 3/20 = 0.15 = 15%
*February 5, 2016*

**precal**

we can pick any direction for the 1st 3 blocks. Say, North. After the 1st 3 blocks N, E and W are interchangeable. Clearly, going N then S will not help, so she can do one of the following: E for 2, N for 1 E for 2, W for 1 E for 2, S for 1 I think you can tell which gives the...
*February 5, 2016*

**Physics**

well, uh, g, just read off the slope and equate it to 1/2 g: 5.00 = 1/2 g g = 10.00
*February 5, 2016*

**Math**

If each line represents 100 sales, then you are correct.
*February 5, 2016*

**chemistry**

wikipedia has a nice article on calcium, and lists several compounds which are essential for good health. Calcium always forms ionic bonds.
*February 5, 2016*

**Math**

Unless it's a large glass, I'd use ounces. Most glasses are 8-12 oz. Of course, those are fluid ounces. Plain ounces are a measure of weight, not volume. A fluid ounce is the volume occupied by one ounce of water.
*February 5, 2016*

**MATH**

google is your friend. I can tell you how, but you can find many illustrated instructions online. Place compass at one end of line segment. Mark an arc with radius more than half the line length. Do the same at the other end. Make sure the arcs are long enough to intersect in ...
*February 5, 2016*

**Physics**

The basic requirement for destructive interference is that the two waves be shifted by half a wavelength. Now, as you know, v = λν, so just plug in your numbers.
*February 5, 2016*

**Math**

just write that in symbols: nth denominator is 3^(n-1) nth numerator is 3^(n-1) - 2 So, the ntheterm is Tn = (3^(n-1) - 2)/3^(n-1) That can be massaged in various ways: Tn = 1 - 2/3^(n-1) Tn = 1 - 6/3^n Tn = (3^n - 6)/3^n
*February 5, 2016*

**shuluka**

Hora aderat briligi. Nunc et Slythia Tova Plurima gyrabant gymbolitare vabo; Et Borogovorum mimzebant undique formae, Momiferique omnes exgrabure Rathi.
*February 5, 2016*

**Complex number**

recall that (a+bi)(a-bi) = a^2+b^2 (1-i)/(1+i) * (1-i)/(1-i) = (1-i)^2 / (1+1) = (1-2i+i^2)/2 = (1-2i-1)/2 = -2i/2 = -i or, 0 - i
*February 5, 2016*