Friday

July 29, 2016
Total # Posts: 42,170

**trigonometry**

sin²(3x) + cos²(3x) = 1 1 + sin²(x) - cos²(x) = 2sin²(x) not zero I suspect you have a typo. A true assertion is sin²(3x) + cos²(3x) - sin²(x) - cos²(x) = 0
*July 25, 2016*

**Math**

just put a 2 in for every x: 7*2^3 + 4 = 7*8 + 4 = ...
*July 25, 2016*

**Math**

don't waste our time posting the exact same problem twice. It is clearly a physics problem, so don;t try to disguise it by calling it just math. Anyone experienced in physics will open the first posting, and help if they can. Anyone not able to help in physics (in this ...
*July 25, 2016*

**math**

Try reading a few of these items. They will be helpful, and explain more thoroughly than you will find here. https://www.google.com/search?q=least+common+multiple&ie=utf-8&oe=utf-8
*July 25, 2016*

**Math**

Type your stuff in at wolframalpha.com. Use parentheses to ensure that its interpretation is what you meant. Check your answer against the one presented. If you can't figure out how to get there, come on back for further help. For #1, see http://www.wolframalpha.com/input...
*July 25, 2016*

**Gemotery**

I disagree. But, I will say that M' = (2,4)*0.8 = (1.6,3.2) You can find others the same way.
*July 25, 2016*

**Chemistry**

how many moles NaOH? how many liters of solution? M = moles/liter
*July 25, 2016*

**physics**

First, check that it hasn't yet hit the ground. Finding it has not, then get the resultant of the horizontal and vertical velocities √(10^2 + (9.8*3)^2) at an angle of 71° below the horizontal
*July 25, 2016*

**business math**

1200(1+.086*6) + 500(1+.086*3) or 1200(1+.086*3) + 1700(1+.086*3) = 2900(1+.086*3)
*July 25, 2016*

**Mathematics @Tris**

Interesting answer. How did you arrive there?
*July 25, 2016*

**Mathematics**

√(61^2 + 28^2) = ...
*July 25, 2016*

**Mathematics**

40/(3+5) = 40/8 = ...
*July 25, 2016*

**math**

6*8^2 = 6*64 = ...
*July 24, 2016*

**math**

A(4) = 80/3 = 26.6666 A(4.01) = 26.6999 slope ≈ .0333/.01 = 3.33 As always, the slope is the rate of change. In this case, how fast the drug is being absorbed 4 <time units> after ingestion.
*July 24, 2016*

**geometrey**

pretty sure it's area.
*July 24, 2016*

**Java**

still Math
*July 24, 2016*

**math**

a graphical or numerical method would do the trick, if you don't have calculus to help.
*July 24, 2016*

**math**

(a) revenue-cost = profit y = p(-(p+5)(p-17)) - (75+12(-(p+5)(p-17))) = -(p^3-24p^2+59p+1095) (b) R>C means P>0 The roots are at -5.2, 13.1, 16.1 From what you know about the shape of cubics, P>0 in the interval (13.1,16.1) (c) y' = -(3p^2-48p+59) y' = 0 at p=...
*July 24, 2016*

**MATH**

check your previous post before reposting the same question: http://www.jiskha.com/display.cgi?id=1469374770
*July 24, 2016*

**Java**

Math class
*July 24, 2016*

**Math**

let u = 9^x then, 9^(2x) = (9^x)^2 = u^2 Thus all you have is u^2+4u = 21 u^2+4u-21 = 0 (u+7)(u-3) = 0 so, u = -7 or u=3 But, u = 9^x ...
*July 24, 2016*

**Math**

this is just a quadratic in 9^x. So, it factors out as 9^(2x) + 4(9^x) - 21 = 0 (9^x + 7)(9^x - 3) = 0 9^x cannot be -7, so you are left with 9^x = 3 x = 1/2
*July 24, 2016*

**Maths**

do a synthetic division on each polynomial using x-p. If p is a common root, then both remainders will be zero. Eliminate p and you will wind up with a polynomial in a,b,c. Solve for b.
*July 24, 2016*

**Some Please Help me - PreCalc**

All you need to do is show that x^2+y^2=1. Don't forget your Algebra I now that you're in pre-cal! (√31/7)^2 = 31/49 (-3√2/7)^2 = 18/49 Looks like they add up to 1, so the point is on the unit circle.
*July 24, 2016*

**Maths**

google is your friend. I found http://math.stackexchange.com/questions/1629163/how-to-find-derivative-of-sin-sqrtx-using-difference-quotient
*July 24, 2016*

**Calculus**

when x=3, y=4 2x dx/dt + 2y dy/dt = 0 or, losing the factor of 2, x dx/dt + y dy/dt = 0 Now just plug in your numbers.
*July 24, 2016*

**Algebra**

well, did you actually try it? 7/6 < 5 check 5 < 1/(1/6) = 6 check So, yes, that works.
*July 24, 2016*

**Algebra**

x + 1.28x = 3420
*July 24, 2016*

**Math**

49 and 0
*July 24, 2016*

**Math**

x(12-x)
*July 24, 2016*

**MATHEMATICS**

4 years ago, the average age was 22. So, now it is 26. After the adoption, since the average age now is 24, The new kid is x years old, where 26*4+x = 24*5 x = 16 So, he was 14 when adopted 2 years ago.
*July 24, 2016*

**Physics**

angular velocity: 2π/40 = π/20 rad/s speed: 40πm/40s = π m/s velocity: -80m/40s = -2 m/s in the direction from start to finish.
*July 24, 2016*

**physics**

p = mv now just plug in your numbers
*July 24, 2016*

**Math**

Assuming the usual sloppiness with parentheses, I parse you equation as (x-1)/(x^2-9) + 1/(x-3) = 2/(x+3) using a common denominator of (x+3)(x-3), we have (x-1) + 1(x+3) - 2(x-3) -------------------------- = 0 (x-3)(x+3) assuming x is not 3...
*July 24, 2016*

**math**

I cannot parse un first second through which height it will move ??
*July 24, 2016*

**maths**

6x + 4y*-3x + 5x - 2x*3y do * first, so 6x - 12xy + 5x - 6xy Now add like terms: 11x - 18xy
*July 24, 2016*

**Math**

distance = speed * time, so if the van's speed is v, then v-28 = 2/3 v
*July 24, 2016*

**Math**

Suppose n groups of beads were used for the necklace. Then 3n yellow beads and 2n blue beads were used. So, counting just the blue beads, 35 + 2n = 4*3n This is not possible if only whole groups of 2 blue and 3 yellow beads were used.
*July 24, 2016*

**Maths & numeracy**

compare $6.48/250g = $.0259/g vs $10.65/375g = $0284/g
*July 24, 2016*

**Maths**

1/x = logn(a) 1/y = logn(c) (x-y)/(x+y) = (1/y - 1/x)/(1/y + 1/x) = logn(c/a)/logn(c*a) logb(c)-logb(a) = logb(c/a) logb(c)+logb(a) = logb(c*a) The two ratios are equal.
*July 23, 2016*

**math**

LCM(6,10) = 30
*July 23, 2016*

**math**

120% = 6/5 y + 6/5 y = 550
*July 23, 2016*

**math**

a 25% increase is a factor of 5/4 So, you need 4/5 of the width for the area to stay the same (5/4 l)(4/5 w) = lw So, what % decrease is 4/5?
*July 23, 2016*

**Math**

see related questions below. Just solve 7.8+3.5sin[pi/6(t-3)] = 10.29
*July 23, 2016*

**Math**

(9^x)^2 + 4(9^x) - 21 = 0 (9^x + 7)(9^x - 3) = 0 ...
*July 23, 2016*

**Math**

300*1.055^n = 3000
*July 23, 2016*

**math**

5/8 - 1/4 = 3/8 So, 3/8 x = 15
*July 23, 2016*

**math**

so what's the trouble? They gave you the equation y = R(p)-C(p) = N(p)*p - C(p) = -p(p+5)(p-17) - (75+12(-(p+5)(p-17))) = (12-p)(p+5)(p-17) - 75 You can expand that if you want. What does it mean? Revenue-Cost = Profit.
*July 23, 2016*

**math**

Fix the typo. And do you mean 6/(2x-y) ?
*July 23, 2016*

**Algebra**

since the area scales by the square of the linear factor, the sides are in the ratio √(32/63) = √(16*2 / 9*7) = 4/3 √(2/7) I'll let you take it from there.
*July 23, 2016*

**physics**

get out your graph paper and plot the motion. Clearly the distance walked is 10+5 = 15 Now, where did he end up? How far is that from where he started?
*July 23, 2016*

**mathematics**

a+9d = 40 + a+4d a+14d = 127 solve for a and d, then find S30 = 30/2 (2a+29d)
*July 23, 2016*

**Math**

x(x+2) = 195 find x, and then x+2 p = 2(x + x+2)
*July 23, 2016*

**Physics**

time to accelerate 10m/s / 4m/s^2 = 2.5s deceleration takes twice as long, since the rate is half as great. Now figure the distance using the good old formula s = vot + 1/2 at^2 for each part of the trip.
*July 23, 2016*

**Math**

good work, but if you are going to include the units in your expressions, it is important to be careful with them: 48hours x 5seconds=240 hour-seconds what you need to do is make sure that the units cancel properly. 48hr x 5s/hr = 240s
*July 23, 2016*

**Linear equations in 1 variable**

Add up their value: 5x + 2(3x) = 77 Now find x and thus 3x.
*July 23, 2016*

**Maths**

2(x+y) = 62 xy = 198 x+y=31 y = 31-x x(31-x) = 198 x^2-31x+198 = 0 (x-9)(x-22) = 0 ...
*July 22, 2016*

**math**

a(bx-c) = d-(x+e) abx-ac=d-x-e (ab+1)x = ac+d-e x = (ac+d-e)/(ab+1)
*July 22, 2016*

**Math**

Hmmm. 7.8sin (pi/6(t-3)) = 10.29 sin (pi/6(t-3)) = 1.319 <--- ?? I suspect that you have left out a term in the definition of h(t). Fix it and then proceed with the solution.
*July 22, 2016*

**Math**

2 trenches = 3*5 = 15 man-hr 7 trenches = 7/2 * 15 = 105/2 man-hr (105/2 man-hr) / (5 man) = 21/2 hr or, 10 hr 30 min
*July 22, 2016*

**RE**

The only thing you have to remember is that since the two sides of an equation are equal (hence the name), if you do the same thing to both sides, they remain equal. Your goal is to isolate the variable on one side, so the other side is just its value. Now, when you say you ...
*July 22, 2016*

**math**

well, you know that the equation for a parabola with vertex at (0,0) directrix y = -p is x^2 = 4py Your parabola has been shifted so the vertex is at (-2,4), so you want (x+2)^2 = 4p(y-4) Your directrix is at y = 1, which is 3 units below the vertex, so p=3 (x+2)^2 = 12(y-4) ...
*July 22, 2016*

**math**

log1/2(x-1)+log1/2(x+1)-log1/√2(7-x)=1 You seriously need to learn how to use parentheses. Also, the final result will depend on the base of the logarithms. I shall assume base 10. Assuming you meant log(1/(2(x-1)))+log(1/(2(x+1)))-log(1/(√2(7-x)))=1 log (1/(2(x-1...
*July 22, 2016*

**Maths**

the height on the nth bounce is 100*0.8^n So, the geometric sequence for the bounces is a = 100 r = 0.8 Each bounce is a round trip, except for the 0th trip, so the distance traveled is 2*100/0.2 - 100 = 900 ft The real-world distance of course will be slightly less than that.
*July 22, 2016*

**math**

the number who passed either or both is 30+20-8 = 42 so, ...
*July 22, 2016*

**math**

or, since 15 = 3*5, multiply by 5/5 and you have 3/7 = 15/x 15/35 = 15/x x = 35
*July 22, 2016*

**Calculus**

well, x is cut off both sides, and x is the box's height, so v(x) = (18-2x)(12-2x)(x)
*July 22, 2016*

**math**

Divide the $420 into 10 parts of $42 each. A gets 3 parts, or $126 B gets 7 parts, or $294 In order for A to get 180, either B gets 420 or a gets 3/7 of the total, not 3/7 of B's share.
*July 22, 2016*

**Futher maths**

I'll just use x, for ease of typing tanx + 2secx = 2cotx + 3cscx A strange mixture of functions, so I'll just use sine and cos: sinx/cosx + 2/cosx = 2cosx/sinx + 3/sinx (sinx+2)/cosx = (2cosx+3)/sinx So, assuming that cosx and sinx are nonzero, sinx(sinx+2)-cosx(2cosx+...
*July 22, 2016*

**Math**

what's the problem? Just calculate the distance and time as needed, and the average speed is distance/time. For (a), A-B is 25km A-C is 10km So, B-C is 15km C-A takes 1.5 hr B-A takes 3.5 hr stop at C takes 0.5 hr So, the B-C leg takes 1.5 hr 15km/1.5hr = 10km/hr The rest ...
*July 22, 2016*

**English**

zombie apocalypse runaway vehicle fire army ants avalanche chainsaw maniac
*July 22, 2016*

**Math**

if you review the definition of the cotangent function, then you can see that with a height of h, h cot19° - h cot37° = 60
*July 21, 2016*

**Physics**

each bulb is a separate branch of the circuit, and so has the same voltage drop. Since they have the same resistance, each bulb gets a current of 1.5V/6.3Ω = 0.238A Note that 1/Rt = 0.317, so Rt = 3.15 = 6.3/2 Ω
*July 21, 2016*

**math**

one measurement is worth a thousand expert opinions. Buy some chips, fill the jar. Empty them out, count them. In the interest of accuracy, it will be best to eat the chips and repeat with a new batch. Maybe several times!
*July 21, 2016*

**Civics.**

I agree with D, but I'd hardly consider Brazil a smaller country. Its area is bigger than the continental USA, and it has vast natural resources. Granted, a lot of them are in the jungle, and that makes them harder to extract.
*July 21, 2016*

**Msth**

actually, keeping track of the units, 1,130mi / 25mi/gal = _______ gallons Multiply the gallons by $2.60/gal to get the dollars
*July 21, 2016*

**Physics**

G(M)(2M)/(3x)^2 = KGM^2/x^2 2GM^2/9x^2 = KGM^2/x^2 2/9 = K
*July 21, 2016*

**statistic**

Consult your Z table to see how many std away leaves 4.5% Multiply that by 0.36 and add it to the mean. Play around with Z table stuff at http://davidmlane.com/hyperstat/z_table.html
*July 21, 2016*

**math**

pair them up in this way: -35,35 -34,34 ... The sum of all those pairs is zero. So, which numbers are left over? Add them up.
*July 21, 2016*

**math**

after a 30% markup the price is cost * 1.30 After a 15% discount, the price is cost * 1.30 * 0.85 = cost * 1.105 That price is $99, so 1.105 * cost = 99 cost = 99/1.105 = 89.59
*July 21, 2016*

**math**

cost * 1.30 * (1-0.15) = 99 cost = 99/1.105 = 89.59
*July 21, 2016*

**Math CSET**

There is no easy way. The actual math formula is simple, but hard to do by hand. I suggest that you just have to know the values for 1,2,3 std from the mean. Just as it is best if you just know the trig values for common angles.
*July 21, 2016*

**Algebra**

Assuming "a rate at x rate per min" means "a rate of x ft per min", then 4000 - xy
*July 21, 2016*

**PHYSICS**

will squash you like a bug.
*July 21, 2016*

**algebra - incomplete**

sorry - you need another equation.
*July 21, 2016*

**Electric Circuits**

I = E/R Now just plug in your numbers.
*July 21, 2016*

**general math**

K(x) = 15.00x for x <= 50 12.50x for 50 < x <= 75 Apparently you had some choices, but they're not here. I got my answer by reading the text provided. How else?
*July 21, 2016*

**math**

LCM(25,30) = 150 minutes 11:00 + 2:30 = 13:30, or 1:30 pm
*July 21, 2016*

**math**

Reiny did this one already. See the related questions below.
*July 21, 2016*

**Physics or Math**

The Toyota goes 350km in 5 hours. The Kia has gone the same distance in 7 hours. So, the Kia's speed must be 50 km/hr
*July 21, 2016*

**math**

for the triangle, 6*5 = 1/2 * 12 * h Now, knowing h, the side length s can be found using s^2 = 6^2 + h^2 For the towers, the distance z is z^2 = 16^2 + (40-10)^2
*July 21, 2016*

**Physics**

distance = time * speed. So, 5*70 = (5+2)*x
*July 21, 2016*

**Calc**

we want to maximize xyz subject to the constraint that 5xy+3(xy+2xz+2yz) = 1000 Using Lagrange multipliers, we find that x=y, and λ=2.1516 and z=4λ That means a local max occurs at (6.455,6.455,8.607) A nice article on Lagrange multipliers, with an example similar to...
*July 20, 2016*

**Geometry**

see earlier post better yet, graph the two functions and see the shifts
*July 20, 2016*

**Geometry**

I think she meant y=(x−5)^2+5 → y=(x−0)^2+0 shift left 5 and down 5
*July 20, 2016*

**Chemistry**

DrBob222 did it last night. See the related questions below.
*July 20, 2016*

**maths - sloppy**

The rectangle is x meters what? wide? long? do you mean x m^2, the area?
*July 20, 2016*

**Math**

There are 4 cubes per foot, so in terms of cubes, the prism is 8/14 x 4 x 5 Since you want whole cubes you are out of luck, since 2/14 < 1/4, the size of a cube. I suspect a typo. Fix it and then apply the logic.
*July 20, 2016*

**Math**

draw your triangle. secθ = r/x and x<0, so θ is in QII or QIII x = -3 r = √20 y = ±√11 Now just recall that tanθ = y/x, so it will be ±√11/3, depending on the quadrant.
*July 20, 2016*