Thursday
February 23, 2017

Posts by steve

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

Algebra
yes
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

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