Monday

January 16, 2017
Total # Posts: 47,898

**Calculus**

You are correct.

*December 22, 2016*

**Maths**

x+100 = 3x+50

*December 21, 2016*

**a.p.**

Surely by now you have some idea how to write the words in algebra. If last year's certificate was worth Rs a, then ar = a + 100 ar^12 = 7200 Now go to work on that.

*December 21, 2016*

**g.p.**

clearly a geometric series. What do you know about them?

*December 21, 2016*

**Physics**

it rose vertically 5/2 meters, so ...

*December 21, 2016*

**Algebra 1**

Since the 18" pizza has 3 times the diameter of the 6" pizza, it has 9 times the area. You'd have to buy 9 small ones to get the same amount of pizza as a large one. so, ...

*December 21, 2016*

**math**

1000(1+.063/12)^19

*December 21, 2016*

**a.p.**

pair them up. (1-2)+(3-4)+... That's basically just n/2 * -1 depending on n even or odd.

*December 21, 2016*

**a.p.**

Sn = n/2 (2*2+(n-1)*3) > 200

*December 21, 2016*

**a.p.**

just add up the two series 2+5+8+...+(3n-1) 3+6+9+...+3n those are easy, right?

*December 21, 2016*

**math**

Huh? The original polynomial? You want (5x^2-3x-9)-(5x^2-3x-9) = 0 now just change the signs of the 2nd polynomial so you can add it instead of subtracting.

*December 21, 2016*

**math**

well, 5 + -5 = 0 -3 + 3 = 0 ...

*December 21, 2016*

**Math**

(8 1/3)(16 1/5)/3 = 45

*December 21, 2016*

**calculus**

40x20

*December 21, 2016*

**ALgebra**

well, it is not linear, since balance increased by 525, then 50 One model (quadratic) is y = -237.5x^2 + 762.5x + 4600 I suspect a typo

*December 21, 2016*

**precalculus**

do you mean your text has absolutely no discussion of this topic? Or that using google produces no results? How about this for such an example? https://www.mathway.com/popular-problems/Calculus/583678

*December 21, 2016*

**Math**

well, p = 2s p + s = 18 Now pick the equation which reflects those facts.

*December 21, 2016*

**algebra @Anneliese**

Actually, besides pointing out the error, I suggested a couple of things for you to use in working the problem. Too bad you didn't make the effort...

*December 21, 2016*

**Science**

speed: 20-at=0 t = 20/a distance: 20(20/a) - a/2 (20/a)^2 = 50-10 a = -5 m/s^2 F = ma = ...

*December 21, 2016*

**Math**

http://www.wolframalpha.com/input/?i=x%5E2sinx%2F1%2Btanx Insert some parentheses to get the interpretation you like.

*December 21, 2016*

**algebra**

you are missing an exponent. t^0 = 1 (4t)^-2 = 1/16t^2

*December 21, 2016*

**math**

n/d becomes .5n/.75d = (.5/.75)(n/d) = (2/3)(n/d) So, it will decrease by 33 1/3 %

*December 21, 2016*

**math college readiness**

the midpoint's coordinates are the average of the endpoints' As you know, the average of two numbers a and b is (a+b)/2 Now you should be able to answer the question with no trouble.

*December 21, 2016*

**math**

how about (-1,1) ?

*December 21, 2016*

**Science**

Nieminen has to travel a distance of (185/2)km at 90km/hr = 1.02777 hours to go. If your statement means that Mäkinen also drove halfway before stopping, then they took 1.3214 hours, so they have to drive 185/2 km in 2*1.02777-1.3214 = 0.734 hours, or 126 km/hr. On the ...

*December 21, 2016*

**math**

24 : 4 + 8 : 2 +2 Not sure what the ratios are doing there, but if we change to the normal fraction notation, 24/4+8/2+2 = 6+4+2 = 12 24/(4+8)/2+2 = 24/12/2+2 = 2/2+2 = 1+2 = 3 24/4+8/(2+2) = 6+8/4 = 6+2 = 8 24/(4+8/(2+2)) = 24/(4+8/4) = 24/(4+2) = 24/6 = 4 You try the others.

*December 21, 2016*

**functions**

x is a function of y, but y is not a function of x. Try graphing it and see that it fails the vertical line test.

*December 21, 2016*

**Math**

16000((1+.05/2)^3 - 1 - .05*3/2) = 30.25 Now, if you meant 3 1/2 years, fix it up.

*December 21, 2016*

**functions**

as written, not, since each x maps to 2 y values. however, y = x+1 is a function, since each x maps to a single y.

*December 21, 2016*

**maths**

hint: (m-n)tan(A+B) = (m-n) (tanA+tanB)/(1-tanAtanB) = (mtanA - ntanB)/(1-tanAtanB) now multiply top and bottom by cosAcosB: = (msinAcosB-nsinBcosA)/(cosAcosB-sinAsinB) the rest should follow without difficulty.

*December 21, 2016*

**Pre - Calc @typo**

Oops I got a and b reversed. http://www.wolframalpha.com/input/?i=hyperbola+(y-1)%5E2%2F64+-+(x-9)%5E2%2F144+%3D+1

*December 21, 2016*

**Math - Trig / Pre - Calc**

the center is at (9,1) a=8 c=4?13 b^2 = c^2-a^2 = 208-64=144 axis is vertical,so (y-1)^2/144 - (x-9)^2/64 = 1 http://www.wolframalpha.com/input/?i=hyperbola+(y-1)%5E2%2F144+-+(x-9)%5E2%2F64+%3D+1 do the other in like wise.

*December 21, 2016*

**Math**

strength, traction and patience

*December 20, 2016*

**math**

I suspect you meant g(x) = 3(x+1) + 6 if so, then A is your answer.

*December 20, 2016*

**Algebra**

these just use the normal sequences of operations... 4(ax+3)-3ax=25+3a 4ax+12-3ax = 25+3a ax+12 = 25+3a ax-3a = 25-12 a(x-3) = 12 a = 13/(x-3) S=180(n-2) S = 180n-360 S+360 = 180n n = (S+360)/180 = S/180 + 2

*December 20, 2016*

**math**

If the box's dimensions are x,y,z, then we have xy = 316 xz = 168 yz = 120 Hmmm. Really? I suspect a typo, since the dimensions are not integers. 316 = 2^2 79 168 = 2^3 3 7 120 = 2^3 3 5 That 79 is a problem.

*December 20, 2016*

**PreCalculus**

log 9?xy = log9 + 1/2 logx + 1/2 logy = 2log3 + 1/2 logx + 1/2 logy or, maybe you meant the 9th root of (xy), in which case we would have 1/9 logx + 1/9 logy

*December 20, 2016*

**Math trig**

Draw a diagram. Review your basic trig functions. It should be clear that the taller tower has height 50 tan36° + 50 tan43° the shorter tower's height is just 50 tan36°

*December 20, 2016*

**Techm**

surely you can use google as well as we...

*December 20, 2016*

**math**

Surely you can at least make a list of values, half of which are less than 30 ... ? Then follow the steps outlined in your previous post.

*December 20, 2016*

**math**

first step: sort the values. Then you can find the mode (most frequent), median (center value(s)), and range (high-low). Then just add them up and divide the sum by how many there are (mean).

*December 20, 2016*

**Math**

height of bars

*December 20, 2016*

**algebra**

c(m) = 15.00 + 0.35m

*December 20, 2016*

**math**

P(1+r)^18 = 10450 P(1+r)^24 = 10600 (1+r)^6 = 10600/10450 r = 0.0023782 Now find P. Note that r is the monthly interest. Adjust to get the annual rate.

*December 20, 2016*

**Riddle**

you have a bed?

*December 20, 2016*

**math**

2(x+2 + x-2) = 48

*December 20, 2016*

**Algebra**

T15 - T7 = 74-34 = 40 = 8d so, d=5 T40 = T15 + 25d = 74 + 25*5 = ?

*December 20, 2016*

**Maths**

good job, except that 2(6+12) = 36, not 30 Should have been 2(x) + 2(2x) = 30 6x = 30 x = 5 sides are 5 cm and 10 cm, with an area of 50 cm^2, and a perimeter of 2(5+10) = 30

*December 19, 2016*

**Math**

This is gibberish. photo? claims? directory? word? session? do you even read what you post? Have you drawn a diagram of the situation?

*December 19, 2016*

**pre calculus**

Clearly the graph is a circle of radius 4 with center at (4,0). You know that r = cos? is a circle with radius 1/2 and center at (0,1/2). so, we have r = 8cos?

*December 19, 2016*

**Algebra**

Apparently, from what you said, X = 168618472 wanna fix what you wrote, and try again, maybe including some info on Z?

*December 19, 2016*

**Algebra**

X=A + B= 168618472 if b = 17472947 than what is A +Z = X what is x

*December 19, 2016*

**Math**

if you want the square root, then that would be 4/7

*December 19, 2016*

**HELP ME PLZ MATH**

21/28 = 7*3 / 7*4 = ?

*December 19, 2016*

**MATH**

(152-133)/10

*December 19, 2016*

**Algebra 1a**

the slope is 7/10 Now just use the point-slope form of the line.

*December 19, 2016*

**Trigonometry**

tan(?-30) = -5 tan 78.7 = 5 since tan? is negative in QII and QIV, ?-30 = (180-78.7) or (360-78.7) so, now you can figure ?

*December 19, 2016*

**Financial mathematics**

P(1+r)^20 = P(1+r)^10 * (1+r)^10 So, the amount after 10 years is 800000/(1+.053/12)^(12*10) = 471433.81

*December 19, 2016*

**maths**

the base has area (40-26)/2 = 7 divide by 2 since the faces come in pairs.

*December 19, 2016*

**chemistry**

first step: what is your balanced equation? then start using moles.

*December 19, 2016*

**Algebra**

#10 wrong -- see #11 #11 right #14 has a typo, but I'm pretty sure you're wrong. #24 what does a tiny correlation coefficient mean? #25 use your favorite best-fit line tool. Many online.

*December 19, 2016*

**Math**

better try using (16,0) and (0,-4)

*December 19, 2016*

**connections math**

x/5 = -2 x = -2*5 x = -10 Ernesto lost 14.5 pounds ... x - 14.5 = 156.5 assuming that he weighed 156.5 after the weight loss The ones you answered you got correct.

*December 19, 2016*

**math(geometric series)**

512/729 = 2^9/3^6 = 2^8/3^8 * 2*3^2

*December 19, 2016*

**tangent help me maths**

you want to find where 2x+5y+11=0 intersects x²+y²+2x-8y-12=0 just doing a straight substitution, we get 4x^2+4y^2+8x-32y-48 = 0 2x = -(5y+11) so, (2x)^2+4y^2+4(2x)-32y-48 = 0 (5y+11)^2 + 4y^2 - 4(5y+11) - 32y - 48 = 0 29y^2+58y+29 = 0 29(y+1)^2 = 0 y = -1 Since ...

*December 19, 2016*

**Algebra**

two exterior angles are also 90° The remaining exterior angles (all the same), are 180-120 = 60° The exterior angles add to 360°, so there are 3 more of them, each 60°. The figure is a pentagon similar to a home plate in baseball. Consider that the interior ...

*December 19, 2016*

**Math**

just mark off any distance x on QR and measure it off 10 times. Let the last point marked be R. Draw line PR. Then construct parallel lines at each marked point on QR, and their intersections with PQ will divide it into 10 equal segments.

*December 19, 2016*

**Math**

I think you can show with little effort that CDEF is a parallelogram. Then find angle ?=DEF of CDEF and its area is 5*5*sin?

*December 19, 2016*

**math**

their sum is ?/2, so if the smaller angle is x, then x + x+2?/5 = ?/2

*December 19, 2016*

**math**

draw an altitude. It forms a 30-60-90 right triangle, where the sides are in the ratio 1:?3:2

*December 19, 2016*

**math**

back it up an hour, and it the same motion as moving from 12:00 to 3:00. Is that easier?

*December 18, 2016*

**geography**

since there are 24 hours in a day (360°), each hour covers about 15°.

*December 18, 2016*

**Geometry**

exterior + interior = 180 The interior angle could be either the vertex angle or one of the two base angles

*December 18, 2016*

**maths**

huh? really? They gave you the numbers! 96:50.40 I guess you could simplify that a bit to 9600/5040 = 40/21

*December 18, 2016*

**Calculus**

depends on the man's height, h. If the shadow's height is s and the light is x m from the wall, then using similar triangles, we have x/s = (x-4)/h x/(x-4) = s/h -4/(x-4)^2 dx/dt = 1/h ds/dt So, plugging your numbers, -4/36 * -1/2 = 1/h ds/dt ds/dt = h/18

*December 18, 2016*

**physics**

draw the diagram. You have a nice 30-60-90 right triangle with a diagonal of 100, so calculating the sides is easy. right?

*December 18, 2016*

**math**

If m=1, you have (x+1)/(x-1) = 1 x+1 = x-1 1 = -1 So, there is no solution, as you already noted. This is made clear when you solve for x: (x+m)/(x?1)=1 x+m = x-1 m = -1 That is the only value of m which works.

*December 18, 2016*

**Math**

the lines intersect at (2,-7). Now just use the 2-point form of the line.

*December 18, 2016*

**unitar**

sounds feasible, all right.

*December 18, 2016*

**Math**

that's what happens when you guess instead of calculate. You are decreasing a larger number, so the % is less: 1.25 * r = 1 r = 1/1.25 = 0.80 = 80% So, you just have to give a 20% discount to get back to the original price.

*December 18, 2016*

**Math**

if y=cost and x=units, then y = 4000 + (30-22)/(6-4) x

*December 18, 2016*

**Math**

y = 1200 + (1350-1200)/2 x Now just plug in x=3 (3 years since 1985)

*December 18, 2016*

**physical science**

PV=kT if T is constant, PV is constant. So, you want 208V = 106*3

*December 18, 2016*

**Math**

The same way I already showed you ...

*December 18, 2016*

**Mensuration**

Just subtract the bare floor from the total area: 10*8 - (10-2*2)(8-2*2)

*December 18, 2016*

**Algebra II Honors**

(25+x)(10+x) = 1000 Or, you could just double the dimensions. Then the area grows by a factor of 4, to 1000 ft^2.

*December 18, 2016*

**Math**

sure. at t=0, we are at the maximum value. But sin(0) = 0 and sin(t) is a maximum 1/4 period later. Go to the website and play around with different shift values. If you replace 3 with 0, you will see that the graph starts at y=10, but we want to shift it so that it starts at ...

*December 18, 2016*

**Math**

I suspect they are expecting you to say the cosine model is simpler, since then there is no shift needed: we start at the max or min. Then all you need is y = ±4cos(?/6 x) + 10

*December 18, 2016*

**Math**

high tide = 14m low tide = 6m so, the center line is (14+6)/2 = 10m, and the amplitude is (14-6)/2 = 4m The 1/2 period (max to min) is 6 hours, so the period is 12 hours. SO, we can start with y = 4sin(?/6 x) + 10 However, sin(x)=0 at x=0 (high tide), and we want y to be at ...

*December 18, 2016*

**Math**

next steps: 2x^2+x-21 = 0 (2x+7)(x-3) = 0 x = -7/2 or 3 since real-world figures do not have negative dimensions, the rectangle is thus 3x7. Which you probably already guessed, since the only factors of 21 are 3 and 7!

*December 18, 2016*

**calculus**

it sure is (x-x^3)-(x^2-x) = -x^3-x^2+2x You can't combine x^2 and x^3 to make x^5!! They're added, not multiplied.

*December 17, 2016*

**calculus**

since f > g on (0,1), the area is just ?[0,1] (x-x^3)-(x^2-x) dx = 5/12

*December 17, 2016*

**math**

Since the diameter is symmetric about (0,0), B=(-3,5)

*December 17, 2016*

**math**

note that y grows by 19 when x grows by 1. So, start with y = 19x Now adjust that so it fits the table.

*December 17, 2016*

**Calculus Finals Review sheet!! Explanation needed**

inflection points are where y"=0. That is, where y' has a max or min. [[x-2]]/x -> [[3.5-2]]/3.5 = 1/3.5 upward acceleration is where the velocity is increasing. That is, where the graph is concave up.

*December 17, 2016*

**algebra**

try typing your expressions in at wolframalpha.com

*December 17, 2016*

**algebra**

without the typo, we have (3x-2)(2x-3) = 3x(2x-3) - 2(2x-3) = 6x^2-9x - (4x-6) = 6x^2-9x - 4x+6 <------- = 6x^2-13x+6

*December 17, 2016*

**Dilation**

just multiply all the coordinates by 2.

*December 17, 2016*

**Go with @Joe**

Sorry about my typo. e^.07t is correct

*December 17, 2016*