Thursday

February 23, 2017
Total # Posts: 48,736

**ellipse - ahem**

b^2+c^2 = a^2

*December 24, 2016*

**algebra**

well, did you try your solution to see whether it works? 3(-5)-(-6) = -15+6 = -9 4(-5)-(-6) = -20+6 = -14 Clearly not. SO, what happened? Using the first equation, we see that y = 3x+9 Using that in the other equation, we get 4x-(3x+9) = -4 4x-3x-9 = -4 x = 5 So, y = 3x+9 = 15...

*December 24, 2016*

**mathematics**

what, you can't plug in the numbers? 1/f = 1/(7/2) - 1/(15/2) 1/f = 2/7 - 2/15 1/f = (30-14)/105 1/f = 16/105 f = 105/16

*December 23, 2016*

**maths 10-3**

(3 ft 2 1/2 in)/2 = (3/2 ft)+(1 1/4 in) = 1 ft 6 in + 1 1/4 in = 1 ft 7 1/4 in

*December 23, 2016*

**algebra**

(t+2v)(t+2v) (z-3)(z+14)

*December 23, 2016*

**math**

just plug into your formula for volume: v = 4/3 * 3.14 * 10^3 = ?

*December 23, 2016*

**Math**

51 = .85x

*December 23, 2016*

**Alegebra**

dilation relative to (0,0) just means you multiply all the coordinates by the dilation factor. You are increasing all the distance from the origin by the scale factor. For example, with a scale factor of 3, (2,-12)->(6,-36) With a scale factor of 1/4, (-12,8)->(-3,2)

*December 23, 2016*

**physics**

maximum range is when the angle is 45° so, minimum velocity need for a given range is at 45° Now just use your range formula using 45° to see what initial velocity has that range. That is your minimum required velocity. Technically, a 1000km range has to include ...

*December 23, 2016*

**Algebra**

y = x+13 y = 2x+5 Looks like x=8 and y=21

*December 23, 2016*

**value**

since distance = speed * time, we need at time t hours 60t = 5(t - 1/3)^2 note: 10 km/hr is speed, not acceleration. I used a = 10 km/hr^2

*December 23, 2016*

**maths**

C is 1/4 of the way from A to B. So, add 1/4 of the difference in coordinates (B-A) to A: C = (-18,8)+(2,-4) = (-16,4)

*December 23, 2016*

**Maths**

The line has slope 3/4 So, the radius has slope -4/3 Thus, the line with that slope through P is y-4 = -4/3 (x+3)

*December 23, 2016*

**Maths**

Suppose the slopes are equal: -k/(k+1) = -4/(3k) -3k^2 = -4k-4 3k^2-4k-4 = 0 (3k+2)(k-2) = 0 k = 2 or -2/3 as you calculated. Using you pairs of equations, we see that they can be written 4x+6y=16 4x+6y=4 2x-y = -24 2x-y = 2 In both cases the lines are distinct and parallel, ...

*December 23, 2016*

**Pre-calc Math**

Draw a diagram. T = top of tree S = tip of shadow B = base of tree Draw a line L horizontally from the tip of the shadow. Drop a vertical from the tree base to intersect line L at P. Let x = SP y = PB h = BT (height of tree) y = 210 sin21° x^2+y^2 = 210^2 (y+h)/x = tan51&...

*December 23, 2016*

**Pre-calc Math**

Draw a diagram. If the height is h, h cot84° - h cot87° = 95 (a) the distance d is found via h^2+(h cot87°)^2 = d^2

*December 23, 2016*

**Pre-calc Math**

sinB/109 = sin24°/78 That gives you B Then C = 180-(A+B) then c/sinC = a/sinA

*December 23, 2016*

**Algebra**

just use the quadratic formula: x = (2a±?(4a^2+16a))/(2a) = (2a±2?(a^2+4a))/(2a) = 1±?(a^2+4a)/a or = 1±?(1 + 4/a)

*December 23, 2016*

**Transformations**

stretch = dilation shift = translation there is no reflection involved. It amazes me that you could not figure that out. I assume you know that x is horizontal and y is vertical...

*December 23, 2016*

**Transformations**

y = 4(2(x-3/2))^2+1 shift right 3/2 horizontal shrink by 2 vertical stretch by 4 shift up 1 or y=16(x-3/2)^2+1 shift right 3/2 vertical stretch by 16 shift up 1

*December 23, 2016*

**SAT Math**

m% of 50 is m/100 * 50 = m/2 20% of n is 20/100 n = n/5 m/2 = n/5 m/n = 2/5 check: m=50, n=125 50% of 50 = 25 20% of 125 = 25 m/n = 2/5

*December 23, 2016*

**math**

3(2tanA)/(1-tan^2A) = 2tanA+1 Now just solve for tanA

*December 22, 2016*

**Grade 6 Maths**

Looks like 7n+1

*December 22, 2016*

**SAT Math Question?**

p-q is largest if p is big and q is small: p-q <= 30-7 = 23 similarly, p-q >= 15-19 = -4

*December 22, 2016*

**Maths - Linear Relations Simple Problem**

if the line intersects, then we have (x-1)^2+5 = mx+2 x^2-2x+6 = mx+2 x^2-(m+2)x+4 = 0 For no solutions, you must have the discriminant negative: (m+2)^2 - 16 < 0 ...

*December 22, 2016*

**math**

z = (148-x-y)^2 x+?y + (148-x-y)^2 = 82 ?x+y + (148-x-y)^2 = 98 now you have just two equations in x and y. Or, assume integer solutions. Then x,y,z must all be perfect squares. Looking at the sums, it should be clear that y>x>z. Now just try a few small numbers. Let z=9...

*December 22, 2016*

**Physical Science**

the equation says that 2 moles of Na react with 1 mole of Cl2 4/2 = 2, so just multiply all the quantities by 2: 4 moles Na react with 2 moles Cl2.

*December 22, 2016*

**Specialist Mathematics**

google "triangle inequality" for many discussions and proofs

*December 22, 2016*

**Algebra 1**

the 3" frame is on both sides, so you need x^2 - (x-6)^2 = 12x-36

*December 22, 2016*

**physics**

his acceleration is 4m/s^2 F = ma 1/10 the time means 10 times the acceleration.

*December 22, 2016*

**co-ordinate geometry**

the locus is a parabola, as you can see from the definitions of the parabola. The directrix is the line x=0. Use what you know about the equation y^2 = 4px In this case, the focus is at (4,0), so the vertex has been shifted to (2,0) and the equation is y^2 = 4p(x-2) Now figure...

*December 22, 2016*

**science**

C=12 O=16 so, ...

*December 22, 2016*

**math**

tan(atan(2/3)-atan(2/5)) = (2/3 - 2/5)/(1+(2/3)(2/5)) = 4/19 = 0.21 as above

*December 22, 2016*

**math**

The figure is a rectangle, since 15^2 + 20^2 = 25^2 The area is thus 15*20 = 300

*December 22, 2016*

**Maths**

27 = s^3

*December 22, 2016*

**math**

see related questions below.

*December 22, 2016*

**MATH**

If he uses x liters of 20%, then the rest (80-x) must be 60%. Now just look at the amounts of acid present: .20x + .60(80-x) = .30*80

*December 22, 2016*

**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*