Saturday

December 10, 2016
Total # Posts: 47,035

**math**

x[(1.12)^(3/2) - (1.12)] = 150 assuming compounding annually

*November 14, 2016*

**math**

Draw a diagram and review your basic trig functions. It should be clear that the height is 15 sin60° + 8 sin30°

*November 14, 2016*

**Calculus**

Looks good to me, but I'd write it as -7/12 ft/s

*November 13, 2016*

**Calculus**

x^2+y^2 = 25 x dx/dt + y dy/dt = 0 So, find y when x=7, and then just use your numbers to find dy/dt

*November 13, 2016*

**Graphing Linear Equations and Inequalities**

while in this case, the explanation gives the right area, technically, the area to the right of the line is x > y/2 Since the y-coordinates are measured vertically, you should be looking for the area below the line. In this case, it's the same area.

*November 13, 2016*

**Math**

x+y+z = 7900 .05x + .11y + .15z = 965 z = x+y + 500

*November 13, 2016*

**Math**

The two roots of 2 and 5 mean y = a(x-2)(x-5)(x-h) for some h. Since y(0)=10, a(-2)(-5)(-h) = 10 ah = -1 Now, fix the bogus (-4) point and see what a and h have to be.

*November 13, 2016*

**Science (galaxies and universe)**

since it takes light some time to arrive at earth, we see what was happening when it left the galaxy, not now. So, if the star is one light-year away, when we see the light, it shows what was happening one year ago. Time travel!

*November 13, 2016*

**Math**

y-k = f(x-h) translates the graph y=x by the amounts h right and k up. y = (x+2)^2-3 y+3 = (x+2)^2 y-(-3) = (x-(-2))^2 so, that is the graph y=x^2 shifted -3 up and -2 right. Or, more simply, 2 left and 3 down. Work the others the same way. You can verify your results at the ...

*November 13, 2016*

**Stoichiometry**

First, balance the equation: 2Al + 3Cl2 -> 2AlCl3 So, you need 3/2 as many moles of Cl2 as you do Al.

*November 13, 2016*

**Integral Calculus**

The p+2 just confuses things. Let q = p+2. Then you have the series 1/1 - 1/2^q + 1/3^q - 1/4^q The alternating series test says this converges for q>0 That is p > -2

*November 13, 2016*

**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*

**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*