Wednesday
December 7, 2016

Posts by steve

Total # Posts: 46,923

Math
which multiple of 3 is 10 more than the same multiple of 2? 3x = 2x+10 x = 10 So, 10 students, 30 pencils.
November 13, 2016

Math
101 102 ... 198 199 and so on up to 904
November 13, 2016

English
#10 should be: Whoa! Bogus, D00d!
November 13, 2016

PreAp Math - incomplete
a. no way to tell, without knowing how many members in the club, or how many times they went shopping in a year. All we know is that some people spent about $18*1.055 each. Big deal.
November 13, 2016

Science-please help
2 and 3 are both involved. If the moon stood still (like the sun) #2 would do it If the earth did not rotate, #3 would still cause the moon to appear to rise and set, but it would only do it once a month, instead of once a day. I think #2 is the best answer here.
November 13, 2016

Math
think about C. It differs from B only in the rate of growth. (100% vs 3%)
November 13, 2016

help me calculus
I'll just use t for ease of typing. Those big Øs just distract me from the math. And that's "pi" not "pai" or "pie" or a dozen other ways it gets misspelled! x = cos(2t) y = 1+sin(2t) dy/dt = 2cos(2t dx/dt = -2sin(2t) dy/dx = dy/dt...
November 13, 2016

NO
?7 is real, but not an integer.
November 13, 2016

Math
assuming you meant the line joining those two points, it is (y2-y1)/(x2-x1) = (6-(-5))/(-4-3) = 11/-7 or, more usually, -11/7
November 13, 2016

8th Grade Pre-Algebra
P' = 1/3 P reflection in the y-axis just changes the sign of all the x-values. Since P" ? P', and P' is smaller than P, P" cannot be ? to P It is, however, similar to P.
November 13, 2016

MATH
clearly not A. 1.5 is real, but not an integer.
November 13, 2016

another please help me check~calculus maths
see related questions below.
November 13, 2016

College algebra
if x at 10%, then the rest (2500-x) at 8%. So, add up the interest: .10x + .08(2500-x) = 2200 But before trying to solve that, think on the numbers. No way could $2500 produce $2200 in interest...
November 13, 2016

Calculus
I guess you did. y' = (8e^(8x))(e^(8x)+9)-(e^(8x))(8e^(8x)) -------------------------------         (e^(8x)+9)^2 = 72e^(8x)/(e^(8x)+9)^2 You can use wolframalpha.com to confirm your results: http://www.wolframalpha.com/input/?i=...
November 13, 2016

Calculus
f = x^3+8x-3 f' = 3x^2+8 f'(6) = 116 dx/df = 1/(df/dx) = 1/116 1/11 must be a typo. http://www.sosmath.com/calculus/diff/der08/der08.html
November 13, 2016

Algebra 2
the real solutions are where the graph crosses the x-axis. That is, where ax^2+bx+c = 0
November 13, 2016

need help calculus plz plz-sir steve
ln(ab+cd) is NOT lna +lnb + lnc +lnd
November 13, 2016

need help calculus plz plz-sir steve
y=3e^(2x)cos(2x-3) y' = 6e^(2x) (cos(2x-3)-sin(2x-3)) y" = -24e^(2x)sin(2x-3) y" - 4y' + 8y = -24e^(2x)sin(2x-3) - 24e^(2x)(cos(2x-3)-sin(2x-3)) + 24e^(2x)cos(2x-3) = 0 Note that the DE y" - 4y' + 8y = 0 has the solution y = e^(2x)(a cos2x + b sin2x...
November 13, 2016

Math
Clearly, k=0 will do the job, but I doubt that's what you want. the quadratic formula says x = (-8±?(64-144k))/72 So, any negative value of k which makes 64-144k a perfect square will work. SO, if we let v be 64-144k, we have k v -1 208 -2 352 -3 496 -4 640 -5 784...
November 13, 2016

Math
That's better. Recall that area = base*height/2 BC is the base, and AD is the height.
November 13, 2016

Math
you have serious notation problems.
November 13, 2016

trigonometry
convert to x-y, add the components, and convert back to compass bearing. 15 @ S40°10’W = <-9.675,-11.463> ...
November 13, 2016

algebraic expression
15-12 and 15+12
November 13, 2016

Tanis
Remember that the circumference is c = 2?r You can find c, and thus get r.
November 13, 2016

Maths
powers of the numbers end in 1: 1,... 2: 2,4,8,6,... 3: 3,9,7,1,... 4: 4,6,... 5: 5,... Note that all can be grouped in periods of 4. 2014 = 4*53 + 2 So, the 2014th powers end in 1,4,9,6,5 Their sum ends in 5 So, the remainder is zero.
November 13, 2016

math
Model using a Venn diagram. The numbers fall into (a) multiples of 6 (b) multiples of 9 (c) multiples of 6 and 9
November 12, 2016

Math
You can't choose both B and D! B grows by a constant 3% rate, or a factor of 1.03 D grows by a constant difference of just 12 Both cannot express the same model.
November 12, 2016

Math- HELP!
Depends on the base of your growth factor. Clearly, the relative amount after t days is 2^(t/3) But, if you want e^(kt), then since 2 = e^ln2, you have (e^ln2)^(t/3) = e^(ln2/3 t) = e^(0.231t)
November 12, 2016

math - typos
fix the typo(s) -/ is not a legal sequence of operators
November 12, 2016

Maths
the series is 132 ?(3k+2) = 3?k + 2?1 k=1 = 3*(132)(133)/2 + 2*132 = 26598
November 12, 2016

maths help sir steve
x^2+2xy+3y^2=1 2x + 2y + 2xy' + 6yy' = 0 (2x+6y)y' = -2(x+y) y' = -(x+y)/(x+3y) y" = -[(1+y')(x+3y)-(x+y)(1+3y')]/(x+3y)^2 You are correct so far. It can be simplified to y" = -2(x^2+2xy+3y^2)/(x+3y)^3
November 12, 2016

Calculus @Multiple Choice!
there you have three answers. Take your pick...
November 12, 2016

Calculus
x^2+y^2 = 20^2 a = xy/2 = x?(400-x^2)/2 da/dt = (200-x^2)/?(400-x^2) dx/dt at x=11, da/dt = (200-121)/?279 * 4 = 18.92 ft^2/s It would have been polite to show your work, so we could find the mistake. Or, of course, check my work to be sure I haven't goofed!
November 12, 2016

math
(x+x+...+x)+(2-1)+(4-3)+...+(100-99) = 0 100x + 50 = 0 x = -1/2
November 12, 2016

maths
we have 3(x-y)^2 (1-y') = A + Ay' 3(x-y)^2 - 3(x-y)^2 y' - A'y = A (3(x-y)^2 + A)y' = -(A+3(x-y)^2) y' = -1 so, y = -x and (2x+(-x))(-1) = (x + 2(-x)) -x = -x Kind of a strange problem. Now for the other one, I'm not sure I can improve on Damon'...
November 12, 2016

Math
You appear to mean "two" distinct real roots, since :tho" is just too weird to mean "one" or "three". SO, there is a repeated root. If the two roots are p and q, with p repeated, then (x-p)^2 (x-q) = x^3-kx+k-1 x^3 - (2p+q)x^2 + (p^2+2pq)x - ...
November 12, 2016

urgent math
In this case, Draw the horizontal ground Draw two vertical lines standing on the horizontal ground, one taller than the other. Label their tops A and B, and their bottoms C and D Draw a horizontal line from the top of the shorter building (A) to where it intersects with the ...
November 12, 2016

urgent math
Draw a diagram and review your basic trig functions. Then it will be clear that if the distance between the buildings is x and the height of the taller building is h, then 39/x = tan36° (h-39)/x = tan47° so, h = (39/tan36°)(tan 47°) + 39
November 12, 2016

math
The 8th term of (a+b)^12 is, according to the binomial theorem, 12C7 a^(12-7)b^7 12C7 ?x^5*(2/?x)^7 = 792 * x^(5/2) * 128/x^(7/2) = 101376/x
November 12, 2016

math
(x+x+x...+x) - (1+2+3+...+10) = 0 10x - 55 = 0 x = 55/10 = 11/2
November 12, 2016

maths too hard help
is that "men or doctors or both"? I assume so, since otherwise, all the doctors are women. It appears that 1 woman is a doctor, since there are only 23 men, 3 of whom are doctors.
November 12, 2016

math- Trigonometry
Draw a diagram. It should be clear that x/15.6 = cos54° If this is challenging, you need to review your basic trig functions.
November 12, 2016

maths sir steve plz reiny plz sir damon plz help
stop with the repeat postings already, ok?
November 12, 2016

maths sir steve plz reiny plz sir damon plz help
?1.21
November 12, 2016

Math
yes.
November 12, 2016

Math
check the slopes. If they are all the same, then the lines are parallel. If their product is -1 (as with -4 and 1/4) then the lines are perpendicular.
November 12, 2016

math
Your average is still 90. The 1.10 (not 1.10%) only matters when weighed in combination with other grades. And even then it might not make a difference. For example, if your other grades are 80 and 100 (with weight 1.00 each), then the average of the three is still 90, ...
November 12, 2016

maths help plz&plz
As you found, 31 play Football and Tennis. But there is no way to know how many play exactly which one sport. Clearly, n can be any multiple of 3. For example, if n=3, then there are 6 people who play exactly one sport, but there's no way to know how those six are ...
November 12, 2016

Maths
h/42 = tan36°
November 12, 2016

English
#1 is best choice. (#3 maybe in Britain) #5 is best match for meaning. #4 implies a lack of specific intent or destination. #6 is just bad usage.
November 12, 2016

English
#1. I don't think that's a good explanation. It just means that I agree. #2 nope - However, it's common to say "It's not raining much"
November 12, 2016

English
yes
November 12, 2016

mathematics
just put the words into math: Original fraction: x/(x+3) (x-2)/(x+3-2) = x/(x+3) - 1/8 Now just solve for x
November 12, 2016

Geometry
opposite angles are equal, and consecutive angles are supplementary, so 3x-20 = 5y-10 7x + 3x-20 = 180 x+y = 30
November 12, 2016

Physical Science
A 68.4-g sample of potassium chloride was added to 200.0 g of water at 20 C. Is the solution saturated, unsaturated, or supersaturated?
November 12, 2016

English
1 and 2 are both common, and mean the same. 3-6 are all grammatically correct, but the only way I'd say it is she is wearing makeup (all finished) she is putting on makeup (in the process) use of the word "cosmetics" in such a context seems stilted to me. The ...
November 12, 2016

math
?(6x-5)/x = 1 6x-5 = x^2 x^2-6x+5 = 0 x = 1 or 5
November 12, 2016

Physical Science
When iron metal reacts with oxygen, the reaction can form Fe203. The balanced chemical equation I think is right is 4 Fe + 302----2Fe203. So I have 4 moles of iron + 3 moles of oxygen creates 2 moles of iron oxide. I need to find the number of moles of oxygen that are needed ...
November 11, 2016

Algebra
the rule of signs says that there is at most one positive root, and 3 negative roots. rational zeros states that any rational root will be ±1 or ±1/2
November 11, 2016

MATH
If x was at 9%, then the rest (700-x) was at 6%. So, add up the interest: .09x + .06(700-x) = 57
November 11, 2016

Math
x = smaller. So, 4x = larger now what else do you know?
November 11, 2016

Linear Algebra
a-3c=0 2b+4c=0 -a+2b+7c=0 3v1 - 2v2 + v3 = 0 v3 = 2v2 - 3v1 ...
November 11, 2016

Math
the diagonal of the square is the diameter of the pizza. ?/4 d^2 - d^2/2 ---------------------- ?/4 d^2 = (?-2)/? = 0.3634 ? 37%
November 11, 2016

Math
look at the diagram. Drop a line from E to AB. E is in the center of the rectangle, so if angle AEB=?, tan(?/2) = (10/2) / (5/2) = 2 ?/2 = 63.4° ? = 126.8°
November 11, 2016

Math
Let the amounts invested at the three rates be x,y,z. Now just write down the facts as given: .04x + .05y + .08z = 5700 x = y + 20000 .08z = 8 * .05y Now just solve for x,y,z.
November 11, 2016

maths
since the terms of the sequence are all odd numbers (2k+1), and there are k^2 terms <= the kth odd number, look for something like 2[?n]+1 That sequence is 3,3,3, 5,5,5,5,5,5,5, ... Looks like we have to adjust it by 1 to get 2[?(n-1)]+1 So, b+c+d = 2 No, I don't have ...
November 11, 2016

Math
3.16 * 10^-23 * 10^9
November 11, 2016

Math
multiply the numbers and add the powers of 10. Use the commutative property of multiplication to rearrange factors as needed. 1.2*10^3 * 1.4*10^2 = 1.2*1.4 * 10^3*10^2 = 1.68 * 10^(3+2) = 1.68 * 10^5 You have to do a final adjustment in some cases to make sure that the number ...
November 11, 2016

maths sir damon help sir steve help sir reiny
If x people play Football and Tennis, then add up the areas of the Venn diagram in the usual way, and you have 2n+19+29-n+x-n=79 x=31 See if that gets you started.
November 11, 2016

Math
Mya gave the time for the whole 1940 miles. But the plane has already gone 400.
November 11, 2016

Math
well, how far does it have to go? time = distance/speed, so ...
November 11, 2016

Science
clearly, 48/500 g/mL = 9.6%
November 11, 2016

plane geometry
what is the perimeter of a 10x11 rectangle?
November 11, 2016

Chemistry
how many kPa in 1 atm? Subtract the sum of all the others from that amount. Then convert back to mm Hg.
November 11, 2016

History | Need help, i'm in a rush =(
probably not A unless you think that the states were sponsoring the escapes.
November 11, 2016

Math
why not 10.84999999999 ?
November 11, 2016

Calculus
you only set f"=0 to find points of inflection. A parabola has no such points. Don't forget your general knowledge of functions in the search for a calculus solution.
November 11, 2016

Math
well, 104 = 2^3 * 13 130 = 2 * 5 * 13 so, find the GCD.
November 11, 2016

maths
(a+b)/2 = (b+c)/2 + 39 a+b = b+c + 78 a-c = 78
November 11, 2016

Physical Science
Materials: Epsom salts (MgSO4), ammonia (NH4OH) small jar or cup measuring cup Procedures 1. Dissolve 1 teaspoon of Epsom salts in a half cup of water. 2. Add 2 teaspoons of ammonia to the Epsom salts solution and stir thoroughly. Record your observations. 3. Allow the mixture...
November 11, 2016

Calculus
profit is revenue - cost P(q) = R(q)-C(q) = 750q - (6000+5q^2) = -5q^2 + 750q - 6000 dP/dq = -10q + 750 So, P is maximuzed when q=75 revenue = cost is the break-even point. Not much profit there...
November 10, 2016

Pre-Calculus
what, forgot you algebra? cosx = -1/2 ...
November 10, 2016

Math
uh, ... 12.4 * 0.42 assuming zero tare weight ...
November 10, 2016

Math
Try using standard ascii characters for your operators: > >= < <=
November 10, 2016

Math
watch the units: 300km/2hr = 300/2 km/hr
November 10, 2016

Math
No way to tell d=0: s > -3 d=-6: s > 3 d=100: s > -103
November 10, 2016

Math
354 and 971
November 10, 2016

math
What do you mean by 1 1/2 times smaller? That's like 150% discount. 100% already takes you down to zero. Do you mean that 2 3/4 is 1 1/2 times a much as you want? If so, then you want 2/3 as much, or 2 3/4 * 2/3 = 11/4 * 2/3 = 22/12 = 1 5/6
November 10, 2016

Math
f(x) = 55
November 10, 2016

college maths
P(1 + .065/4)^4 = 1600
November 10, 2016

Math
Or, just find the cube roots of your numbers. For example, ?60 = 3.91 so, it is between 3 and 4, since 3^3 = 27 4^3 = 64
November 10, 2016

Math
start listing the cubes: 1: 1 2: 8 3: 27 ... Then pick the two numbers from column 1 that correspond to the cubes near your targets in column 2.
November 10, 2016

pre-calculus @Damon is right
Sorry - I missed the -2 ; read x=2
November 10, 2016

pre-calculus
(A) y = 1/(x-2)(x-5) (B) y = (x+3)^2 / (x-2)(x-5) (C) y = 3(x+3)^2 / (x-2)(x-5)
November 10, 2016

math
T1 = 12 Tn = (-1)^n * |Tn-1| - 3
November 10, 2016

Math
If the side is x cm, then 4(x-2*4)^2 = 144 Or, since the height of the box is 4 cm, and 144/4 = 36, the final base of the box is 6x6 cm. That makes the original size 14x14
November 10, 2016

math help
google is your friend. Just look for "fractions math examples" and you will get lots of hits.
November 10, 2016

pls help!!! -- typos galore!!
#1 (a) unbalanced parentheses 9>4t<l) ?? both f and t a d l? Fix the typos and try again. Use * for multiplication online. And 7-+4 is probably better just as 7-4 (unless you meant something else) #2 google makes a good calculator. But even without it, the only numeric ...
November 10, 2016

physics
The induced emf in a coil is equal to the negative of the rate of change of magnetic flux ... So, if the flux increases, the emf decreases, but the absolute value increases.
November 10, 2016

math
Try this instead: I know how to spell, and I know grammar. Here is the sentence again: "Hi, I am of no help to you because I don't know the answer. Sorry, hope you pass the class." and by the way, sorry for having fun (_><_); it's not a privilege, it&#...
November 10, 2016

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