Sunday
March 1, 2015

Posts by Steve


Total # Posts: 29,297

Math
7*9+7 = 63+7 = 70
January 15, 2015

Math
that is correct, but to follow the advice given, you should have taken the following step: 43+9 = j-9+9 That gets rid of the 9 from one side and leaves j all alone: 52 = j That is the result you wanted, not just rewriting it with the solution inserted. When it says to solve ...
January 15, 2015

Math
8000(1+0.11/2)^(2*8) = ?
January 15, 2015

math
a = (5-2x)(3-2x) a = 12
January 15, 2015

Math
just set 4x = 2x^2 4 = 2x x = 2
January 15, 2015

Math - oops
y(-1) = -2
January 15, 2015

Math
you ever gonna show any of your work? you want the slope of the line (-2) to be the same as the slope of the parabola. The slope of the parabola at any point (x,y) is 6x+4 So, if 6x+4 = -2, x = -1 y(-1) = 6, so the line y = -2x+b must pass through (-1,-2) I think now you can ...
January 15, 2015

Math
downstream speed: 10/(1/2) = 20 mi/hr upstream speed : 10/(5/6) = 12 mi/hr So, if te boat's speed is b and the current's speed is c, b+c=20 b-c=12 now go figure c
January 15, 2015

Position vs. Time graph clarification
it is a parabola, just like the trajectory of a falling body under constant gravitational acceleration.
January 15, 2015

algebra
0.80c + 50 = 1.05c c = 200
January 15, 2015

Math
Divide the octagon into 8 congruent isosceles triangles, each with base 15. Since the vertex angle is 360/8 = 45°, each of the slant sides has length 7.5/sin22.5° = 19.6 The desired distance is twice the length of one of these sides, or 39.2
January 15, 2015

algebra
no access to those files. Better just give some coordinates. Then use the 2-point form of a line to get the equation.
January 15, 2015

MAT222
since 27 = 3^3, 27^(1/3) = 3 27^(2/3) = 3^2 = 9 So, you have 27^-(2/3) = 1/27^(2/3) = 1/9 the other is correct
January 15, 2015

alegbra 1
a little less work would be to note that if you subtract one equation from the other, the x's disappear: x+y=5 x-3y=3 4y = 2 y = 1/2 Then use that value of y in either equation to get x.
January 15, 2015

chemistry
2H2 + O2 = 2H2O 10g of H2 is 5 moles. Each mole of H2 produces a mole of H2O, so, you will get 5 moles of water. Just convert that to grams for the mass.
January 15, 2015

math
2500/25 = 100 m^2 since a = pi r^2, pi r^2 = 100 So now you can easily find r.
January 15, 2015

math
a+b = 8 10a+b + 18 = 10b+a Now just solve for a and b, the two digits.
January 15, 2015

solid mensuration
since s = rθ, r = s/θ = 112/(28 * π/180) = 229m
January 15, 2015

MAth Igcse
If we label the top of the tower T and the bottom Q, then we have tan 27° = PQ/QA tan 11° = PQ/QB QA^2 + QB^2 = 40 (PQ/tan27°)^2 + (PQ/tan11°)^2 = 40^2 Now just solve for PQ, the height of the tower.
January 15, 2015

solid mensuration
the area, of course, is base * height = 225*80 = 18000m^2 Use the law of cosines for the diagonals. The angles between the sides are θ and π-θ, where sinθ = 80/145
January 15, 2015

precalculus
so, use the product-to-sum property: sina cosb = 1/2 (sin(a+b)+sin(a-b)) with a=x+y and b=x-y, that gives 1/2 (sin(2x)+sin(2y)) Not sure why you would have used up so much paper, given that they told you what formula to use...
January 15, 2015

calculus
I always hate to see homework dumps. I'll do a couple, but till I see some work on your part, I feel no obligation to do all your work. #1 f(x) = cos(x) f'(x) = -sin(x) at the given point, f'(2) = -sin(2) #2 Recall that |x| = x if x >= 0 |x| = -x if x < 0 At ...
January 15, 2015

algebra
Hmm. It occurs that you might have meant that 4b = b+12 so, b = 4 baby is 4, sitter is 16
January 15, 2015

algebra
s = 4b+12
January 15, 2015

Science Ms. Sue?
Looks like C to me A: winter is approaching B: ditto D: either a day or a year has passed, depending on the revolution. C happens as the axis tilts toward the sun, which would cause all the effects listed.
January 15, 2015

calculus
homework dump alert! I did a couple of these above. Do you have any ideas of your own we can check?
January 15, 2015

Algebra
well, divide each term by 3x^2 6x^3/3x^2 = 2x 24x^2/3x^2 = 8 So, the result is 2x-8
January 15, 2015

math
(3/4)(15/2) = 45/8 or 5 lb 10 oz
January 15, 2015

math
(4.50/60 * 25.0 * 5280)/45.0 = 220 cars
January 15, 2015

math
Hmmm. 36+48 ≠ 72 also, 6in/72mi is a scale of 1:760320
January 15, 2015

math
clearly, it is 6in:72mi Now you just have to figure out how many inches in 72 miles and rewrite the scale in just inches. (B) 2 inches on the map. 1/3 as far on the map, 1/3 as far in real life: 24 miles.
January 15, 2015

math
first get rid of the (x-y): (x-y)(4(x-y)^2-1) Now you have a difference of two squares, so (x-y) (2(x-y)-1) (2(x-y)+1) ...
January 15, 2015

Math
that would be a good first step.
January 14, 2015

trigonometry
Consider your answer. The angle traverse is quite small. Will it really rise more than its entire length? Draw a diagram. after swinging through an angle θ, the distance from the top is 1.8cosθ. So, the amount it has risen is 1.8(1-cosθ) I suspect you used r(1+...
January 14, 2015

Math
ln 35.3595 = 152r
January 14, 2015

Math
Both look good to me, but not sure about #1.
January 14, 2015

Logarithms
since log_u(x)/log_v(x) = log_v(u) and log_u(x) = 1/log_x(u), we have log_a/b(a) = 1/log_a(a/b) = log_a(a) + log_a(1/b) = 1 + log_a(1/b) If those two properties of logs have not yet been delivered to you, work to convince yourself that they are true. I'm sure you can find ...
January 14, 2015

math
Looks like C to me 6/12 = 1/2 = 1:2 2.5/5 = 1/2 = 1:2
January 14, 2015

Math
once the two checks have cleared, his balance at the bank will be 56.75 - 5.00 - 13.25 = 38.50 His checkbook shows 87.37-38.50 = 48.87 more than that. Looks like (A) as you said.
January 14, 2015

math
Just write what that means: .36x = 25200 So, divide by the 0.36
January 14, 2015

math
since y can be expressed in two ways, set them equal: 4x = 2x^2 4 = 2x x = 2 Now you can find y easily.
January 14, 2015

math
equate the two functions, since they are both y: 8x+7 = -x^2-5x+7 x^2+13x = 0 x(x+13) = 0 . . .
January 14, 2015

math
that would be where 9x-4 = x^2+7x x^2-2x+4 = 0 That has no real solutions, so I suspect a typo. See that the graphs do not intersect: http://www.wolframalpha.com/input/?i=plot+y%3D9x-4+%2C+y+%3D+x^2%2B7x Now, the line y=9x+4 does intersect the parabola.
January 14, 2015

calculus - oops
d/dx cos^-1(x) = -1/√(1-x^2)
January 14, 2015

Algebra 1
The size of a certain cell is 2.5 * 10 to the -9 power m. Another cell is 1.5 * 10 to the 3rd power larger. How large is the larger cell in scientific notation? my answer is 3.75 * 10 to the -6 power m
January 14, 2015

Algebra 1
What is the simplified form of (-3x to the 3 power y squared) (5xy to the -1 power)
January 14, 2015

Algebra 1
What expression is equal to 1/8000 written in scientific notation? My answer is 1.25X 10 to the negative 4 power.
January 14, 2015

Math
since the cord costs less than $1/meter, and you bought less than 5 meters, how can it cost more than $5? 4.58 * 0.98 = 4.49 How did you come up with $5.83?
January 14, 2015

Math
6(4) + 6(x) = 24+6x
January 14, 2015

math
0.9p = 1.08c p = 1.08/0.9 c = 1.2c so, the price is a 20% markup before discount
January 14, 2015

math
commutative property is for addition and multiplication. I guess it also applies to Boolean logic, but I fail to see how your "answer" relates to that. I ate dinner and read a book. is the same as I read a book and ate dinner.
January 14, 2015

math
you are correct
January 14, 2015

math
log(u/v * s/t) = log(su/tv)
January 14, 2015

math
well, start listing them: p = 1 n = 5 d = 10 q = 25 pp = 2 pn = 6 ... ppnnndqq = 77 Now count them up, after eliminating duplicate amounts
January 14, 2015

Algebra 1
(-m) to the-3 power n if m =2 and n = -24
January 13, 2015

Algebra 1
Thank you
January 13, 2015

Algebra 1
Simplify -(14x) to the 0 power y to the -7 power z
January 13, 2015

math - pls check!!!
looks good, except for the standard form. That would be 3x + 8y = 23
January 13, 2015

math
these are the squares of 2,3,5,7,11,13 An odd sequence, unless you note that these are the primes. The next prime is 17, so the next term is 289
January 13, 2015

Math - Trigonometry
If you understand since functions, you must understand this. The height of a point on a rotating circle is ha sine (or cosine) function. The question does not state at what point to start measuring, so we will start with the car at its lowest point at t=0. Since cos(t) is a ...
January 13, 2015

maths
v = 4/3 pi r^3, so the tank can hold 1/2 * 4/3 * pi * (3/2)^3 = 7.07 m^3 of water So, it will take 7.07 m^3 / (25/7 L/s) to drain I'll let you do the conversion from m^3 to liters.
January 13, 2015

Algebra
do a little multiplying and you have 8h + 6f = 16.80 15h + 6f = 27.30 Now subtract to get rid of the f's and you have 7h = 10.50 h = 1.50 Now you can figure f.
January 13, 2015

math
If there are m math questions which take 2x minutes each, and e english questions which take x minutes each, 2xm + xe = 60 2xm/xe = 8/7 14xm = 8xe 7xm=4xe 7m=4e m+e = 22 x(2m+e) = 60 x(8m+4e) = 240 x(15m) = 240 xm = 16 2xm + xe = 60 32 + xe = 60 xe = 28 xm+xe = 22x 16+28 = 22x...
January 13, 2015

math
don't be put off by all the words. Just write each fact down as math. You have several amounts: a,b,c,e,g. 2a = 3c = 4e 5b = 6e = 8g Since the LCM(2,3,4) = 12, 2a,3c,4e must be a multiple of 12 Since LCM(5,6,8) = 120, 5b,6e,8g must be a multiple of 120 Now, if 4e is a ...
January 13, 2015

Math
the LCD is 4x. So, that gives you 2(x-3)/(4x) - x(4x+3)/(4x) = [2(x-3)-x(4x+3)]/(4x) = (2x-6-4x^2-3x)/(4x) = -(4x^2+x+6)/(4x) That's about as far as you can take it.
January 13, 2015

Algebra
#1 is an example of why we always set factored expressions to zero. If the product of several factors is zero, one of the factors must be zero. So, we must have one of the following: x^2+5 = 0 Cannot happen x^4+3 = 0 Cannot happen 100x^2-10 = 0: x = ±1/√10 100x^2+...
January 13, 2015

Math
correct!
January 12, 2015

Math
x + x+13 = 93
January 12, 2015

Calculus
Hmmm. I'd say it's 12 feet tall h = 12
January 12, 2015

Math
If $x is at 7.5%, then the rest (10000-x) is at 9%. So, add up the interest: .075x + .09(10000-x) = 849 ...
January 12, 2015

Calculus
oh, come on. f' is the slope of f. So, if f' > 0, f is increasing. f" indicates concavity. If f" > 0, the graph of f is concave up. Have you not read any of your text?
January 12, 2015

Calculus
in general, you cannot. You can, however, tell where f' is positive or negative or zero, or where f" is positive or negative or zero.
January 12, 2015

Math
Nope. (-2)^2 = (-2)(-2) = +4 Similarly, (-y^2)^2 = (-y^2)(-y^2) = +y^4
January 12, 2015

math
well, how many different ways can the dice turn up? How many of those have two 1's?
January 12, 2015

MATH
You have a point (15,450) and a slope (4), so the line should be p-450 = 4(x-15) I'd say (B) with a typo
January 12, 2015

Math stem question
the equation is correct.
January 12, 2015

Math
(50/x)*80
January 12, 2015

Geometry
since the arc lengths are the same, 90r = 60w So, r/w = 2/3 Since the areas vary as the square of the radii, R/W = = (r/w)^2 = 4/9
January 12, 2015

Math
3s+9c = 75 8s+5c = 67
January 12, 2015

Math
correct
January 12, 2015

Algebra
-2 ≤ d + 0.5 ≤ 4.5 -2.5 ≤ d ≤ 4.0
January 12, 2015

Math
so, did you use your calculator? What did you get? Just plug in the numbers as given you.
January 12, 2015

Math
If 6 are boys, then the other 12 are girls, so 12/18 = ...
January 12, 2015

AP Physics
all the kinetic energy is converted to potential energy, so 1/2 mv^2 = mgh or, h = v^2/2g
January 12, 2015

math
in hundredths, you have 8/100 60/100 70/100 Looks like they're already in order...
January 12, 2015

Math
well, just plug in t=3
January 12, 2015

Algebra
y = 1/3 x + 26/3
January 12, 2015

Algebra
just look up the point-slope form. You will see that the equation is y+2 = 1/2 (x-5)
January 12, 2015

Math
the speed (distance/time) is constant, so that means 5/37 = 25/m None of the choices matches that exactly, but it is easy to see that (C) is the same equation.
January 12, 2015

Math
If you really want to use the index as you did, just type 2root or 3root. "square root" always means index of 2.
January 12, 2015

Math
in that case, yes. If there is no index, 2 is assumed. Online, its usually better to say sqrt for square root cbrt for cube root 4throot, 5throot, etc. x^(1/n) for the nth root. It's too easy to mistake the desired index for a multiplier.
January 12, 2015

Math
the two temperatures are equidistant from their average, (10.4+7.6)/2 = 9.0 So, you have |t-9.0| = 1.4
January 12, 2015

To: Anonymous and all others
Well done, student! These are model posts of homework problems. The problem is clearly written, possible answers are given (optional, of course), and the student's answer is noted, along with an indication of the solution method. If actual work had been shown, that would ...
January 12, 2015

math
1/12 + 1/x = 1/4 x = 6 so, 6 hours for the friend.
January 12, 2015

Math
well, since 0.7 = 7 * 0.1, add up seven times 1/10 of 0.7. That is, divide the 0.7 into ten equal pieces, and add up 7 of them. divide 1/4 into 5 equal pieces. Add up 4 of them.
January 12, 2015

algebra 2 help
3|x+4| = 8 |x+4| = 8/3 so, x is 8/3 away from -4, either + or - A is the solution to |x+4| = 6 or 3|x+4|=18 B is the answer to |x| = 2 C is the answer to |x+4| = 15 D is the answer to |x+18| = 4 If you have a typo, the answer may be (A) And if you can't even spell "...
January 12, 2015

chemistry
does HCl dissolve Al2O3? It probably reacts with it, instead. If that's what you meant, then figure how many moles of Al2O3 you have, then check the reaction to see how many HCl it takes to react with one Al2O3. Then you will need that many moles of HCl. Convert that back ...
January 12, 2015

Maths literacy, accounting, economics and business studies
It certainly looks like good preparation. Especially the Accounting course ...
January 12, 2015

physics
Since there are 86400 seconds and 40030 km in the earth's circumference, the plane must travel 40030/86400 km. Assuming east-west travel at the equator. I assume that the question is ignoring the truly minuscule relativistic effects of such a slow speed. Also, what are the...
January 12, 2015

Please check my Calculus
all look good to me. No reason to be unsure on #2. Just the chain rule. If u = 3x, y=sec u y' = secu tanu u'
January 12, 2015

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