Wednesday

May 25, 2016
Total # Posts: 40,789

**Brief Calculus**

f' = 12x^2 - 18x - 30 Now use your Algebra I skills. (A) the critical numbers are where f'=0 (B) f is increasing where f' > 0.
*April 1, 2016*

**precalc**

Using the usual formulas, sin42°+sin18° = 2 sin30° cos12° since sin30° = 1/2, that is just cos12° = sin78° cosine means sine of the complement.
*April 1, 2016*

**Math**

if the drawing is 1 x 1.25 inches, then clearly each inch represents 20 feet.
*March 31, 2016*

**Math**

multiply all the numbers by 7 so that the largest is 42. 14:21:35:42 that should help.
*March 31, 2016*

**Mathematics**

so, if you plug in 12 for t, how do you get 12/3 = 15? You apparently did 12+3=15 better review what the operators mean.
*March 31, 2016*

**Mathematics**

well, it's bogus. It's already a whole number of dollars. Rounding to the nearest dollar doesn't mean anything unless there are some cents. $2200.51 rounds up to $2201 $2200.23 rounds down to $2200 $2200 rounded to the nearest thousand is $2000
*March 31, 2016*

**Math**

Draw a diagram. If the base of the rectangle is the segment (a,0) to (b,0) then the upper vertices are (a,4a) and (b,6-5b). Since it is a rectangle, the height is the same, so 4a = 6-5b. That is, b = (6-4a)/5 Now, the area is (b-a)(4a) = ((6-4a)/5-a)(4a) = 12a/5 (2-3a) This is...
*March 31, 2016*

**pr calc 11**

The quadratic formula works with all quadratics!! h = -0.09x^2+x+1.2 h(x) = 0 when x = [-1±√(1^2-4(-.09)(1.2))]/(2(-.09) = (-1±√1.432)/-0.18 = -1.09 or 12.20 Now, how does that answer the question? It means that when the water shoots out, it will hit ...
*March 31, 2016*

**pr calc 11**

just solve h(x) = 0
*March 31, 2016*

**algebra**

Since time = distance/speed, d/24 + 1/6 = d/30
*March 31, 2016*

**Math 142 (Pre-Cal) (Circles)**

looks good to me.
*March 31, 2016*

**math help pls pls pls**

correct.
*March 31, 2016*

**math help pls pls pls**

Assuming you know what the standard form is (highest degree first), then can you determine the degree of each term? Just add exponents of all the variables. what if two terms have the same degree? I have checked a few discussions, and none mentions that wrinkle. Check your ...
*March 31, 2016*

**algebra**

just sub in2x+2 for y x^2+3x-4 = 2x+2 x^2+x-6 = 0 (x+3)(x-2) = 0 ... or, without solving, you could just check each of the choices... duh
*March 31, 2016*

**Math**

If the sides in order of length are a,b,c then b = a+7 c = b+2 = a+9 a^2+b^2 = c^2 a^2+(a+7)^2 = (a+9)^2 a=8, b=15, c=17 I think you can take it from there, right?
*March 31, 2016*

**Hi need help with math**

what's all this shape stuff?
*March 31, 2016*

**algebra**

all those words! f(x) = |x| if -3 <= x < 1 4 if 1 <= x <= 8 Just plot each line, and mark off the sections you want. http://www.wolframalpha.com/input/?i=plot+[piecewise+[{{|x|,+-3%3C%3Dx%3C1},{4,+1%3C%3Dx%3C8}}]]
*March 31, 2016*

**College Algebra/pre-calculus**

since the value starts at $8000 and decreases by 7000 in 10 years ($700/year), the equation for the value is y = 8000 - 700x at x=6, y = 8000 - 4200 = 3800
*March 31, 2016*

**math**

a constant rate (slope) means a linear function. So, which of those is linear?
*March 31, 2016*

**Math**

of the 52 cards, how many are a heart or a 10?
*March 31, 2016*

**math**

P(pop) = 9/92 so, P(0 pop) = (83/92)^13 P(1 pop) = 13C1 (9/92)(83/92)^12 add them up
*March 31, 2016*

**vectors**

suppose we say that vectors u = force of 125 N pulls due west v = force of magnitude v pulls N 28.79 W r = resultant force is 212 N at angle b expressing those in x-y coordinates, u+v = r <-125,0> + <-v sin 28.79,v cos28.79> = <212 cosb, 212 sinb> <-125,0&...
*March 31, 2016*

**Algebra 2**

correct all the way. Good work.
*March 31, 2016*

**Geometry**

.015mi * 5280 ft/mi / .005hr * 1hr/60min * 1rev/2πft = 414.69 rev/min
*March 31, 2016*

**Solid Mensuration**

what is the cross-section?
*March 31, 2016*

**Geometry**

a = πrs, so 46πs = 736π s = 16
*March 31, 2016*

**Math**

1/42^42
*March 31, 2016*

**Algebra**

x + x/7 = 88
*March 31, 2016*

**simple interest**

since 12% is 2/3 as much interest, 3/2 as much should be invested there. Or, since the interest ratio is 2:3, the investment should be 3:2 So, 40% at 18% and 60% at 12% .12 * 7200 = .18 * 4800 = 864 or, in the usual algebraic way, .12x = .18(12000-x)
*March 31, 2016*

**simple interest**

.09x + .15(14000-x) = 1800 better check your work
*March 31, 2016*

**simple interest**

mine, too
*March 31, 2016*

**simple interest**

.10x + .12(8000-x) = 900
*March 31, 2016*

**MATH**

After you arrive at an answer, you need to do a sanity check. Your answer makes no sense. The problem says that the membership rose by 30% to 182. So how can you possibly accept the answer that last year it was 425? a proportion needs two ratios or fractions: 182/x = 1.30/1.00
*March 31, 2016*

**math**

1.25^2 = 1.5625 why do you say that 3.14 * 1.25^2 = 1.5625? (a) where does 1.11803 come from? (b) how can you say with a straight face that 10*1.11803 = 33.20? You have some serious problems here, either with calculation or typing.
*March 30, 2016*

**geometry and trig**

not sure what you're doing wrong, because you haven't said what you are trying to do. But if you want the side length, then if it is s, then you do have (s/2)/9 = sin(22.5) s = 18*.3826 = 6.888
*March 30, 2016*

**Real Analysis (Math)**

since the limit on the left is 0 and on the right it is 1, There is clearly no L such that limit(delta->0) |f(x)-epsilon| < 0 if |x-0| <= delta
*March 30, 2016*

**Math**

you might consider carrying the units along at each step. (d m)/(400 m/min) = d/400 min Makes sense, since distance/speed = time Using your equations, multiplying 6 min * 400m/min = 2400m makes sense, since the distance d is in meters.
*March 30, 2016*

**precalc**

(2^(3+h) - 2^3)/(8h) = (8*2^h -8)/(8h) = 8(2^h - 1)/(8h) = (2^h - 1)/h f(x) = 2^x g(x) = √(x-7) (g◦f)(5)/(f◦f)(3) = √(f(5)-7)/2^(f(3)) = √(2^5-7)/2^(2^3) = √(32-7)/2^8 = 5/256
*March 30, 2016*

**Trigonometry**

the gradient is the slope, is the tangent of the angle. So, tan(theta) = y/x = 0.700/-0.714 find theta. It will be in QII
*March 30, 2016*

**Math**

since time = distance/speed, d/400 + d/80 = 6
*March 30, 2016*

**Math**

base area = B face area = 2B total surface (two bases + 3 faces): 2B + 3(2B) = 80
*March 30, 2016*

**Physical Science**

The voltage across each resistor is the same: 120V then, for each resistor Ri, the current is Ii = 120/Ri amps
*March 30, 2016*

**algebra**

y^a * y^a + 2 y^(2a) + 2 Not sure where you want to go with that. or, assuming the usual carelessness with parentheses, y^a y^(a+2) = y^(2a+2) = (y^(a+1))^2 = (y^2)^(a+1)
*March 30, 2016*

**Math**

there are only two choices π*2^2*9 = 36π π(9/2)^2*2 = 81/2 π The radius will be half the rolled dimension.
*March 30, 2016*

**ALGEBRA ONE**

correct.
*March 30, 2016*

**ALGEBRA ONE**

the first and last numbers must be perfect squares. So, B is out. The middle number must be twice the product of the roots of the 1st and last, since (a+b)^2 = a^2+2ab+b^2 If we check 9x^2+9x+1, a=3 and b=1, but that would need 2*3*1 = 6x in the middle. So, (A) is out. Check ...
*March 30, 2016*

**alg**

No. (x+4)(x-4) = x^2-16 (x-4)(x-4) = x^2-8x+16
*March 30, 2016*

**Math**

AB = 5 AC = √85 BC = √40 Call the angle x. Then by the law of cosines, 40 = 25+85-2*5√85 cos(x)
*March 30, 2016*

**Algebra 1-Factor by Grouping Help!**

I'll admit that if the question is unclear, so will be the answer. Better check with your teacher.
*March 30, 2016*

**Algebra 1-Factor by Grouping Help!**

Well, there must be a typo somewhere, because if we say -7+49 = 42, then we have 3u^2-21u+42 and that does not factor.
*March 30, 2016*

**Algebra 1-Factor by Grouping Help!**

since you have 3u^2, look for multiples of 3: 3u^2-21u = 3u(u-7) Work on that idea. But why both the -7 and +49 constant terms? Looks like a typo to me.
*March 30, 2016*

**ALGEBRA**

HUH? I told you which one. See any minus signs anywhere?
*March 30, 2016*

**ALGEBRA**

since the 1st and last are perfect squares, look for (3x+7)^2 = 9x^2+42x+49
*March 30, 2016*

**algebra**

Since it is a perfect square, it's easy to check. (a-b)^2 = a^2-2ab+b^2 so you know that a=3 and b=1 (3x-1)^2 = 9x^2-6x+1
*March 30, 2016*

**Math**

If there were m monkeys, then the rest (24-m) were lions. m = 3(24-m) ...
*March 30, 2016*

**Math**

22.00(1+.06875)
*March 30, 2016*

**Math**

1:150 / 1:300 = 1:150 * 300:1 = 2 2x2 = 4
*March 30, 2016*

**math**

S = 80/2 (7+393)
*March 30, 2016*

**algebra**

-16 + m^2 - 6m m^2 - 6m - 16 so, what two factors of 16 differ by 6? (m-8)(m+2)
*March 30, 2016*

**Math algebra**

well, 36 = 2^2 * 3^2 Not sure what that has to do with x,y,z
*March 30, 2016*

**Geometry**

The diagonals bisect each other, and are perpendicular. So, drawing the diagonal of 14, you have two triangles with base 14 and altitude 1/2 of the other diagonal. So, if the other diagonal has length 2x, then 2( 1/2 * 14 * x) = 31 x = 31/14 and the other diagonal is 31/7 ft
*March 30, 2016*

**College algebra**

How many pounds of nuts selling for$6/lb and raisins selling for $3/ lb should a person combine to obtain150 lb of trail mix selling for $4/lb?
*March 30, 2016*

**mathematics-calculus-derivatives**

do you mean the 5th derivative? d5y/dx5? dy/d(5x) = 1/5 dy/dx If that makes any sense. start taking derivatives -- you will see a pattern.
*March 30, 2016*

**maths**

The question makes no sense. It will "look" 1.9m wide from any distance. There must be more to the question.
*March 30, 2016*

**math**

since time=distance/speed, 25/x + 1 = 30/x x = 5 some slow rider!
*March 30, 2016*

**math**

you got rid of the subtraction by adding. Get rid of the division by multiplying. m/5 * 5 = 29*5 m = 145
*March 30, 2016*

**math**

CD has slope 2/3 so, QC has slope -3/2 CD: y+6 = 2/3 (x+3) CQ (since it contains point C): y+6 = -3/2 (x+3) At x = -1, y+6 = -3/2 (-1+3) y+6 = -3 y = -9 Q is thus (-1,-9)
*March 30, 2016*

**arithmetic progression**

a(a+3d) = 70 (a+d)(a+2d) = 88 Since 88=8*11, I'd guess that T2=8 and T3 = 11 so, that makes T1=5 and T3=15 or, you can solve the equations using algebra.
*March 30, 2016*

**Math**

recall the formula: v = 1/3 pi r^2 h Now just plug in your numbers.
*March 30, 2016*

**trignometry**

well, recall that (tanx + cotx)^2 = tan^2x + 2tanx*cotx + cot^2x
*March 30, 2016*

**math (algebra 1)**

60(1+.10)^3 = 79.86, but that is how much will be in the account. As you note, only $19.86 of that is the interest, which answers the question asked.
*March 30, 2016*

**pr calc 11**

(x+2)^2-(x+2)-42 Note that (u-7)(u+6) = u^2-u-42 So, letting u=x+2, we have (x+2-7)(x+2+6) = 0 (x-5)(x+8) = 0 as above
*March 30, 2016*

**Calculus**

y = √(x+√(x+√(x+...))) y^2 = x+√(x+√(x+...))) y^2 = x+y 2yy' = 1+y' y' = 1/(2y-1) = 1/[2√(x+√(x+...)))-1]
*March 29, 2016*

**Math**

you are correct.
*March 29, 2016*

**maths**

theta, not thita. I'll just use x. You want sin x = 0.5623 Since sin is positive in QI and QII, and sin(34.2°) = 0.5623 the solutions are x = 34.2° and 180-34.2°
*March 29, 2016*

**pre calc 12**

well, just solve for t when -5t^2 + 12t + 2 = 12 But I suspect a typo, since the maximum height reached is 9.2m ??
*March 29, 2016*

**Algebraic**

x^2-6x - 12 (x^2-6x+9) - 12-9 (x-3)^2 - 21 so, setting (x-3)^2 - 21 = 0 (x-3)^2 = 21 x-3 = ±√21 x = 3±√21
*March 29, 2016*

**algebra**

such as ... ?
*March 29, 2016*

**math**

so, you have the numbers and the formula. What's the trouble?
*March 29, 2016*

**Math**

You are correct. The function should be h(t) = 25t - 5t^2 The -5t^2 term is due to the downward pull of gravity. The +25t indicates an initial upward velocity.
*March 29, 2016*

**Cartesian Equation**

see a good discussion of a similar problem here: http://math.stackexchange.com/questions/199475/find-an-equation-of-the-plane-passing-through-2-points-and-perpendicular-to-anot google is your friend.
*March 29, 2016*

**math**

you want to find $/g. So, start working with the units: 12.0gal/66lb * 3.50 $/gal * 1lb/454g = $0.0014/g or .14¢/g
*March 29, 2016*

**math**

j = 2s j = m-2 m = s+7 So start substituting till you get to j.
*March 29, 2016*

**math**

13+5M
*March 29, 2016*

**Math**

If x gallons of apple, then 2x + 3.50(10-x) = 26
*March 29, 2016*

**geometry**

C = 180-55-44 = 81 Since AB is side c, the law of sines tells us that AB/sinC = b/sinB Now just plug in your numbers.
*March 29, 2016*

**Geometry**

Check your formula for the area of a cone. A = πr^2 + πrs where s is the slant height: √(r^2+h^2) So now, just plug in your numbers.
*March 29, 2016*

**Math**

lots of resources online. Google is your friend.
*March 29, 2016*

**math**

78 / 9 x 3 + (6 - 9) 78 / 3 + (-3) 26 - 3 23 Note that I did (1/9 * 3) first, due to the fact that 78/9 is not an integer, but 78/3 is. (78/9)*3 = (78*3)/9 = 78*(3/9) = 78/3
*March 29, 2016*

**Check My Answer! :)**

If the height of each triangular face is 4, then the area including base is 36 + 4*6*4/2 = 84 without the base, it's 48 If it is 5, then the area is 36 + 4*6*5/2 = 96 without the base, it's 60 So, you can see that much important information has been omitted. The answer...
*March 29, 2016*

**Check My Answer! :)**

what is the difference between altitude and height? 144 = 36 + 4*27 I can't "square" that with the dimensions given, assuming the base is 6x6. So, what's the difference between the height and the altitude?
*March 29, 2016*

**Calc 2**

If you want an explicit function, then you are correct.
*March 29, 2016*

**Calc 2**

du/dt = (2t + sec^2(t))/(2u) 2u du = (2t + sec^2(t)) dt u^2 = t^2 + tan(t) + c 16 = 0+0+c u^2 = t^2 + tan(t) + 16
*March 29, 2016*

**Calc 2**

yes.
*March 29, 2016*

**Calc 2**

dy/dx = x/y y dy = x dx y^2 = x^2 + c 49 = 0 + c c = 49 y^2 - x^2 = 49
*March 29, 2016*

**Math**

LCM(44,56) = 7*8*11 So, there will be 14*44 by 11*56 = 616x616 mm, using 14*11 = 154 tiles
*March 29, 2016*

**Mathematics**

so, did you do it?
*March 29, 2016*

**Math**

S150 = 150/2 (2*15 + 149*2)
*March 29, 2016*

**physics**

If I understand conservation of energy correctly, if her weight is mg, then the loss of PE going from 2m to 1m is mg Joules. So, since that is converted to KE, we have mg = 1/2 mv^2 2g = v^2 v = √19.6 m/s
*March 29, 2016*