Sunday
February 19, 2017

Posts by STEVE

Total # Posts: 48,624

algebra
Not sure just what your f(x) is, but for any inverse function g(x) = f^-1(x), (f?g)(x) = (g?f)(x) = x
January 29, 2017

Algebra
Your syntax is cockeyed Correct the typos and try again a^b4^c6^ is gibberish a8^b2^c3^ is gibberish What does 6^ mean? Ah. Maybe you mean -3a^8 b^2 c^3 (5abc^9 -11a^ b^4 c^6) At this point I have to stop. I can't parse the 2nd factor.
January 29, 2017

calculus
you know that lim(u->0) sinu/u = 1 let u = 2/5 x lim sin2x/5x = lim sinu/(5/2 u) = lim sinu/u * 2/5 = 1 * 2/5 = 2/5
January 29, 2017

des school
tsa is total surface area. r=8 v = pi r^2 h = 288pi so, h = 288pi/64pi = 4.5 tsa is two circles plus the curved sides: 2pir^2 + 2pi r h = 2pi*r(r+h) = 2pi*8(8+4.5) = 200pi cm^2
January 29, 2017

math
using Taylor series, sinx-x = -x^3/3! + x^5/5! - ... x-tanx = -x^3/3 - 2x^5/15 - ... divide both by x^3 and you have -1/3! + x^2/5! - ... -1/3 - 2x^3/15 - ... now divide and let x->0 and (-1/3!)/(-1/3) = 1/2
January 29, 2017

calculus
That is, http://www.jiskha.com/display.cgi?id=1485688337
January 29, 2017

calculus
see your other post for the method.
January 29, 2017

calculus
lim(x -> -1+) x^2 = 1 ax+b = -aa+b when x=-1, so lim(x -> -1-) = -a+b So, we need -a+b = 1 f(-2) = -2a+b = -1 So, now we have two equations for a and b, giving us a=2 and b=3 So, f(x) = 2x+3 for x > -1 Now the limit from both sides at x = -1 is 1 and f(x) is ...
January 29, 2017

calculus
lim (x->1) = -2 g(1) = 0 So, there is a jump discontinuity. It is not removable, since g(1) is defined, but is not the same as the limit from both sides.
January 29, 2017

calculus
ok. there is certainly a break at x=1.
January 29, 2017

Math
1.06 * 0.97 = 1.0282 so, it grew by 2.82%
January 29, 2017

Math
a+2d = 20 a+13d = 64 11d = 44 d=4 a=12 Tn = 12 + (n-1)*4 = 8+4n
January 29, 2017

math
s+t = 27 t-7 = 3+(s-7)/4 ...
January 29, 2017

math
n = -2m, so m+2(-2m) = 3 -3m = 3 m = -1 n = 2
January 29, 2017

Math
3x-4=29
January 29, 2017

Precalculus
since cos(4t) has period pi/2 and sin(6t) has period pi/3 the LCM is pi
January 29, 2017

math
36/720 = 1/20 = 5% absent. So, ...
January 29, 2017

Math
this is just a right triangle with longest leg length 4. (Hypotenuse is 5) 5+3+4 = 12 180/12 = 15 So, scale it up by a factor of 15, and its sides are 75:45:60
January 29, 2017

math2
just use the power rule. For example, a. v(t) = 2t+3 v(2) = 2*2+3 = 7
January 29, 2017

Math
?(-3/2 * 81) = 9?(3/2) i ?(-3/(2*81)) = 1/9 ?(3/2) i = 1/(3?6) i = 1/18 ?6 i
January 29, 2017

maths
how far have you gotten using Reiny's suggestion? For #2, you might also look at it as involving the translation of one line onto a parallel line. The line from (-2,3) to (3,4) is one side of the parallelogram. If you translate (-2,3) to (-3,-2) then you have moved it by...
January 28, 2017

Pre Cal 12
900(1+r/4)^(4*12) = 1400 r = .0369 ? 3.7%
January 28, 2017

Pre Cal
f(x) = (x-3)^2(x-2)+c Note that 3^2*2 = 18 But that will be -18 (why?), so c=36 and that's "constant" not constance.
January 28, 2017

Calculus can you please show me the step by step s
As Tom showed you, I = A/s^2 + 8A/(600-s^2) Actually, that is not quite right. It should be 1/s^2 + 8/(600-s)^2 You should have caught that. In any case, The A is just a constant, so it does not affect the solution, and we can say I = 1/s^2 + 8/(600-s)^2 dI/ds = -2/s^3 + 16/(...
January 28, 2017

Math
|T-88| <= 7.5 88-7.5 <= T <= 88+7.5 ...
January 28, 2017

Maths
well, 2x = 25-5y So, use that: 4x-3y = 11 2(2x)-3y = 11 2(25-5y)-3y = 11 50-10y-3y = 11 -13y = -39 y = 3 Now use that to find x.
January 28, 2017

Math show work
Using convenient units of 1 AU for earth orbit and mass of sun=1, and P=1 earth year, you know that R^3 = P^2 using 11.1P, (11.1P)^2 = 123.21P^2 = (4.976R)^3 So, the distance is 4.967 AU
January 28, 2017

Math
recall that cot -x = -cotx = -1/tanx
January 28, 2017

Math
well, ? radians = 180 degrees 4.5 rad * 180deg/? rad = ? deg
January 28, 2017

Mean (Average) Question
How come you have only 9 values, if you have ten lions? Surely the 10th litter is also zero? In any case, the mean is the sum divided by the no. of values being measured.
January 28, 2017

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

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