Thursday
February 11, 2016

Posts by STEVE

Total # Posts: 37,554

Math
Don't worry about finding negative square roots. Every square root has a corresponding negative root. That is because if the positive root is n, Then n^2 is its square. (-n)(-n) = n^2 also gives the same value when squared. So if you find that 4^2= 16, (-4)^2 is also 16. ...
January 14, 2016

Geometry
use the point-slope form of the line: y-0 = 2(x-4) or y = 2x-8 Now, check the choices and see which one works when used in that equation.
January 14, 2016

Geometry
a-b < c < a+b Looks like A to me. D is wrong, because if c=9 or 25, the triangle is just a flat line. Try drawing it.
January 14, 2016

MATH HELP FAST AND I MEAN NOW I NEED THE ANSWER!!!
Is that Fahrenheit or Celcius degrees?
January 14, 2016

Calculus AB
v = πr^2h dv = 2πrh dr + πr^2 dh h is assumed exact, so dh=0. dv = 2πrh dr dr = 0.2, so dv = 2π(4)(12)(.2) = 19.2π and that's ± Your estimate assumes that the height was also measured with an error. The problem does not say that. If ...
January 14, 2016

Math
it works just like a rectangle: 2(12+x) = 42
January 14, 2016

Geometry
Yes, it certainly is confusing.
January 14, 2016

math
well, just expand and equate coefficients: 2x^3 +7x^2-x-6 = Ax^3+(AB-A+1)x^2+(B+3-AB)x+(-B-C) So, you have A = 2 AB-A+1 = 7 B+3-AB = -1 -B-C = -6 A=2, so you have 2B-2+1=7, so B=4 That better work with B+3-AB = -1 4+3-2*4 = -1 -- check -B-C = -6 -4-C = -6 C=2
January 14, 2016

Homework for Math
ax^2 + bx + c = 0 a(x^2 + b/a x) = -c x^2 + b/a x = -c/a x^2 + b/a x + (b/2a)^2 = (b/2a)^2 - c/a (x + b/2a)^2 = b^2/4a^2 - c/a (x + b/2a)^2 = (b^2-4ac)/4a^2 x + b/2a = ±√(b^2-4ac)/2a x = [-b±√(b^2-4ac)]/2a
January 14, 2016

math
just expand the right side and the equate coefficients of like powers. If the polynomials are identical, all the powers of x must have the same coefficients. You can see right off that the right side will have 2Ax^2+... So, 4 = 2A and A=2 and so on.
January 14, 2016

Math
take a look at the sum (a1-a2)+(a2-a3)+...+(a98-a99)+(a99-a100) Everything cancels out except a1 - a100
January 14, 2016

Possessive form
looks good to me.
January 14, 2016

AAHOOOOGAAAHH! Homework Dump!
You not gonna provide any effort at all?
January 14, 2016

math
no idea, but they add up to 90 degrees.
January 13, 2016

Pre- Algebra
sort of. Multiply each item's price by the quantity of that item. That gives the amount spent for that item. Then add up the products to get the total amount spent. 24.95x + 4.75x + 29.99*1 That can be simplified into 29.70x + 29.99
January 13, 2016

Geometry
ummm, that's the definition of a parallelogram.
January 13, 2016

Math
See http://www.jiskha.com/display.cgi?id=1452644352
January 13, 2016

algebra 1
since distance = speed * time, if the boat's speed is b and the stream's speed is s, 7(b+s) = 280 14(b-s) = 280 b+s = 40 b-s = 20 b=30, s=10
January 13, 2016

Calculus AB
How do you get g(2x)=8 at x=1? g(2) = 4 Anyway, take a peek here and I think it will become clear. Just be sure to include that final 2 for the g(2x) instead of g(x). http://www.calculus-help.com/6-table-derivatives/ scroll down to the end.
January 13, 2016

Algebra
google is your friend
January 13, 2016

math
since 24 is the LCM of 6 and 8, cut each piece into 3rds. Then there are 24 pieces, and each person gets 4.
January 13, 2016

Math - typo
somehow the √13 became √3, but I'm sure David can fix that, eh?
January 13, 2016

Math
because the ratio of the change in y to the change in x is constant. Draw any two right triangles whose diagonal is a section of the line, and they are similar, since the have common angles.
January 13, 2016

Math Help!
assuming you mean two 5's, then they add up, making 10N.
January 13, 2016

Math
h = 2f+3
January 13, 2016

math - bogus
Not only is your sentence incomplete, but you provide no information as to the scale of the map. try proofreading your posts...
January 13, 2016

math
Assuming that the present will actually fit within the box, then the empty space is the difference between the volumes: 2.5 * 2 * 1.5 - 3 = ?
January 13, 2016

Math
6*6*6*6 = 6^4
January 13, 2016

Math
if 100 is 35% of the price, then the original price is 100/.35 = $285.71 so, ...
January 13, 2016

Math
the depreciation factor is r, where r^6 = 2800/31000 = 0.090 The value after 3 years is thus 31000 * r^3 = 31000 * √.09 = 31000 * .3 = 9300
January 13, 2016

Math
There are 5! = 120 ways to arrange 5 subjects. Now, the 6th subject (which just happens to be one of the 5 as well) can be inserted in any place in the schedule. So, there are 6 places to insert it. The 6th subject can be any of the 5, so there are 5 ways to choose it. So, ...
January 13, 2016

math
come on, do some thinking. If a number is divisible by 5, it must end in 5 or 0. In this case, 5 must be the 3rd digit. That leaves 2,3,6,7,9 for the other two digits. So, there are 5 ways to pick the 1st digit. Once it has been picked, there are only 4 choices for the 2nd ...
January 13, 2016

Algebra
(a) no solutions. How can 4x-y be both -1 and -3? (b) many solutions: if you multiply the first equation by 2, you will see that both equations describe the same line. Google is your friend. Use it to get lots of examples of linear equations in problems. To solve by graphing, ...
January 13, 2016

Math/Physics
Draw a diagram. Review the definition of the cotangent. If the height is h, then h cot19° - h cot23.8° = 910
January 13, 2016

Math
what? eh? huh? Mark point T (the tee) Mark point H (the hole) Draw the line TH. Draw angle at T 21° from the line TH. Mark point (B) on that line roughly 3/5 as far from T as H is. Can you see the triangle?
January 13, 2016

Geometry
No idea, since you do not describe the figure.
January 13, 2016

science help
data is information. A is redundant. I'd say D.
January 13, 2016

Math
why can you not just say x/3 instead of the "over"? sheesh. -9p-17 = 10 -9p = 27 p = -3 x/3 - 10 = 12 x/3 = 22 x = 66 and so forth.
January 13, 2016

Vector and scalar quantity
3,5 - 4,3 = -0,8 so the resultant points to the left. I expect you can draw your own diagrams. Oh, wait -- maybe not, or you'd have seen the answer already...
January 13, 2016

Math Correct Me!!
The common multiple is 3, because 12*3 = 36 see http://www.phschool.com/iText/mgmath_course2/Ch05/05-04/PH_MSM2_ch05-04_Obj1.html and scroll down a bit. 4/5 = x/27 4*27 = 5x x = 108/5
January 13, 2016

Algebra
Try plotting the points. Note that (3,2) and (3,-9) form a vertical line of length 11 The point (2,-9) is one unit away, so you have a triangle with base 11 and height 1. Now, is that so hard?
January 13, 2016

math
.75x + 2 = .80x Now you can find x
January 13, 2016

Maths
After t hours, the distance d can be found by d^2 = 15t^2 + (5-10t)^2 2d dd/dt = 30t + 2(5-10t)(-10) 2d dd/dt = 230t-100 dd/dt = (230t-100)/(2d) since d is never zero, that means dd/dt=0 when t = 10/23 hours
January 13, 2016

Mathematics, Vector, Physics
come on. That's just 70 sin45° a wind from the southeast is blowing northwest
January 13, 2016

Mathematics, Vector, Physics
Let's see what I get h = 375.877i+136.808j w = -49.497i+49.497j so, v = 326.380i+186.305j = 375.810 @ 60.28° and those are headings, not bearings!
January 13, 2016

Math
Oops. that's 30θ = π
January 13, 2016

Math
s = rθ Plugging in your numbers, 60θ = π
January 13, 2016

math
I think you need to explain a bit more. Clearly the equation as written is false.
January 13, 2016

math
well, AB=15, so draw the triangle and it will be clear.
January 13, 2016

Maths
Do you mean r = -(1/2)^n?
January 13, 2016

Algebra
If their ages are x,y,z then we have z = y-4 y = 2z Clearly, Joe is 4 and Kyle is 8 so, ...
January 13, 2016

Math
9.96^2 = 99.2 in^2 24 ft^2 = 24*144 = 3456 in^2
January 13, 2016

math
If there is a common ratio, then you need (2x+4)/(6x+12) = (x-7)/(2x+4) x = 25 So, the common ratio is 54/162 = 1/3 Since |r| < 1, the sequence converges.
January 12, 2016

algebra
x^-2y = y/x^2 6z^-1 = 6/z If you want a single fraction, then that would be (yz+6x^2)/(x^2z)
January 12, 2016

Calculus - Finally!
1/2 log(u^2/(1-u^2)) 1/2 log(sin^2(x/2)/cos^2(x/2)) log(tan(x/2)) -log(cot(x/2)) -log((1+cosx)/sinx) -log(cscx+cotx)
January 12, 2016

Calculus
Well, I made a blunder, but you should have caught it. dx = 2/cos(x/2) du so, the integral becomes ∫ 1/2sin(x/2) * 1/cos(x/2) * 2/cos(x/2) du = ∫ 1/(u(1-u^2)) du = log(u) - (1/2)log(1-u^2) = (1/2)log((u^2/(1-u^2)) I feel that is headed somewhere we want. As usual, ...
January 12, 2016

calculus
dv/dt = 1.6t^3/√(0.2t^4+8100) Let u = 0.2t^4+8100 du = 0.8t^3 dt Now you have dv/dt = 2du/√u v(t) = 4√u + c = 4√(0.2t^4+8100) + c Now plug in your numbers to find c, and then find v(10).
January 12, 2016

Math
512 = 8^3 so the area is 6*8^2 Just to be precise, volume is not measured in cm^2.
January 12, 2016

Math
(n+2)^2 = 2n^2 - 1 You might think that it would be possible for n to be even, but since the right side must be odd, so must n^2 be odd, and thus any solutions you find will be odd.
January 12, 2016

i need help
that's one way.
January 12, 2016

i need help
d/12 = 24.5/7
January 12, 2016

Algebra
94 + x <= 110
January 12, 2016

math help please
since d = kf, d/f = k and is constant. So, you want d such that d/12 = 24.5/7
January 12, 2016

Math
the numbers are 1,5,9,... The nth white bead is bead number 4n-3
January 12, 2016

math help
10m = 1000 cm So, multiply the drawing dimensions by 1000.
January 12, 2016

Calculus AB
Maybe you have heard of Rolle's Theorem, a special case of the MVT.
January 12, 2016

maths - incomplete
depends on how much per ounce the 16-oz jar costs. Figure that out, subtract 5 cents, and then multiply that by 24 oz.
January 12, 2016

Math
which number has only two pairs of factors?
January 12, 2016

Math
#1. Nope. Add 7 to both sides #2. Nope. What is 5.5-4.5 again? #3. Nope. Subtract 12 from both sides #4. Nope. At least means not less than, right? Batting a big zero on this one.
January 12, 2016

Algebra
if the width is w, then the length is 200-w. (why?) the area is w(200-w). Can you take it from there?
January 12, 2016

Math
75 * 1.20 = 90
January 12, 2016

Calculus
800 @ 140° = <514,-613> 130 @ 27° = <59,116> So, you want <x,y> such that <x,y>+<59,116> = <514,-613> Once you have x and y, then convert back to speed and heading.
January 12, 2016

maths
it will float if its density is less than water's (1g/cm^3) so, figure your density and then answer the question.
January 12, 2016

Math
3x/3 = x so, ...
January 12, 2016

math
Since constants cannot intersect lines or parabolas in infinitely many points, and lines cannot intersect parabolas in more than two points, D is the only choice: the two expressions describe the same parabola.
January 12, 2016

Geometry 1 question
just use your distance formula. Or, the Pythagorean Theorem. Plot the points. The distance you want is just the hypotenuse of a right triangle with legs 8 and 3. So, it is √(8^2+3^2) Better study your material some more.
January 12, 2016

MATH help
B is exactly the opposite of true. The output depends on the input. Try C. Usually when making a table, you list the values of the independent variable, and then figure out the dependent values in column 2.
January 12, 2016

Algebra help help!!!
4^x-3^(x-1/2)=3^(x+1/2)-2^(2x-1) 4^x - 3^x/√3 = √3 3^x - 4^x/2 (3/2) 4^x = (√3+1/√3)3^x (3/2) 4^x = (4/√3) 3^x (4/3)^x = (8/√27) (4/3)^x = (4/3)^(3/2) x = 3/2
January 12, 2016

PHYSICS
there is no atom just free electrons which disperse or are attracted by some other charged particles
January 12, 2016

Physics Component Method
the components are (just as in polar coordinates): x = r cosθ y = r sinθ You have r and θ, so plug and chug.
January 12, 2016

Shurley English
true, but the words are preposition, noun, noun, conjunction, pronoun, verb, adjective, adjective, noun, preposition, noun.
January 12, 2016

Algebra
If there are x multiple-choice questions, then there are 15-x open ones. 4x + 12(15-x) = 100
January 12, 2016

Calculus help!!!
good luck with that! since e^u is always positive, you need y>0 and x>0 Since e^xy > 1, and grows very fast, I seriously doubt that x^2y will ever catch up, and sinxy is insignificant. Let y=0 or x=0 x^2y+sinxy=0 but e^xy=1 You can see that the slope of x^2y+sinxy is ...
January 12, 2016

math
b/g = 2/5, so 5b=2g g = b+9 Now just solve for b and g.
January 12, 2016

Trigonometry - wow!
Good luck with that! I have no clue how to get an exact solution. The graphs at wolframalpha.com and the analysis provided there don't give me much hope: http://www.wolframalpha.com/input/?i=2tanx+cos2x%2B1%3Dtan3x%2B2cos2x
January 12, 2016

Homework for Math
park area: 60*100 = 6000 If the terrace has uniform width w, then garden area is (60-2w)(100-2w) (60-2w)(100-2w) = 3000 Now just solve for w.
January 12, 2016

Maths
LCM(5,6,8) = 120 So, every 120 seconds they all fire together.
January 12, 2016

Calculus
Let x be the number of price decreases. Then the revenue is r(x) = (900-100x)(5000+1500x) = 100*500(9-x)(10+3x) = 50000(-3x^2+17x+90) Now find when dr/dx=0 and you can figure the price for maximum revenue.
January 12, 2016

Calculus
I'd say the critical point exists, since the usual definition that y'=0 or is undefined. In either case, I think that (3,0) is the critical point.
January 12, 2016

calculus
d/dx f^2 = 2f df/dx ∫ lnx/x dx Since we are discussing f^2, let's let f(x) = (lnx)^2 df/dx = 2 lnx * 1/x = 2lnx/x So, clearly, ∫lnx/x dx = (lnx)^2/2 + C check, using integration by parts: u = lnx dv = dx/x du = 1/x dx v = lnx ∫lnx/x dx = lnx*lnx - ∫...
January 11, 2016

Calculus
well, from the graph at http://www.wolframalpha.com/input/?i=+2+cos%28x%29+%2B+%28cos%28x%29%29^2 I'd say you were wrong. f = 2cosx + cos^2(x) f' = -2sinx - 2sinx cosx = -2sinx(1+cosx) f'=0 where sinx=0 or cosx = -1 x = 0 or pi
January 11, 2016

Calculus
1/2 ∫ 1/(sin(x/2)cos(x/2))dx let u = sin(x/2) du = 1/2 cos(x/2) dx or, dx = 2/cos(x/2) du Then you have 1/4 ∫1/u 2/(cos(x/2))dx = 1/4 ∫ 1/u du = 1/4 ln(sin(x/2)) + C Now, we all know that ∫ csc(x)dx = -ln(cscx + cotx) so what gives here? 1/4 ln(sin(x/2...
January 11, 2016

Mathematics
If there were x correct answers, then there were (120-x) incorrect answers. So, x - (120-x)/4 = 80
January 11, 2016

math
clearly the radius of the circle is 3. So, what is pi * 3^2 ?
January 11, 2016

Math
you know that tan(x) -> ∞ as x -> π/2 so, what do you think?
January 11, 2016

math 1
4":14' = 4":(14*12)" = 1:42
January 11, 2016

math 1
error was 10 10/85 = ?
January 11, 2016

Math
not differentiable if f'(x) is undefined. f'(x) = 1/√(1-x^2) so f' is undefined at x=±1 Now review the principal values of arcsin(x) cusps and corners are not differentiable, since the limit of f' is not the same from both sides.
January 11, 2016

math
since each triangle has sides 1/2 as big, the areas are 1/4 as big. So, just form a G.P. of the desired quantities and work with that.
January 11, 2016

Math
a+c = 9 8a+5c = 54
January 11, 2016

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