Wednesday

January 18, 2017
Total # Posts: 47,946

**Math**

R*I = I ? is irrational I+I = I (usually) R^3 = R so ok there

*December 2, 2016*

**Algebra**

do you know the golden ratio?

*December 2, 2016*

**algebra 2a solving systems using matrices**

Nope. The matrix has no x in row 1.

*December 2, 2016*

**Math**

cos(180-x) = -cos(x) cos(90-x) = sin(x) so you have (0.5)cos^2(x)sin^2(x) = 0.05 cos^2(x) sin^2(x) = 1/10 sin^2(2x) = 1/40 sin(2x) = ±1/(2?10) ...

*December 1, 2016*

**Pre-calc**

one revolution covers 26? inches. Now let's start the conversion. 70mi/hr * 1hr/60min * 5280ft/mi * 12in/ft * 2?rad/26?in = 5686 rad/min

*December 1, 2016*

**Math**

200*20^2 = 200*400 = 80,000 if the answer is -8000 then there has been some mangling. It seems clear that something is wrong, since ()^2 is always positive.

*December 1, 2016*

**math**

Draw a diagram. The angle ? subtending the visible part of the earth is such that cos(?/2) = 1/3 see what you can do with that.

*December 1, 2016*

**Algebra**

visit here for all the details: http://www.mathportal.org/calculators/polynomials-solvers/synthetic-division-calculator.php

*December 1, 2016*

**Algebra**

try here: http://calc101.com/webMathematica/long-divide.jsp

*December 1, 2016*

**deferential calculus**

where is the wall? at the circumference of the courtyard?

*December 1, 2016*

**math**

standard form is just 9.26

*December 1, 2016*

**math**

9 + .2 + .06 = ...

*December 1, 2016*

**Math**

the quotient of x + 2 is incomplete. You need the quotient of ... and ... since division needs a divisor and a dividend.

*December 1, 2016*

**Math**

the areas are in the ratio 3^3:5^2 = 9:25 = 108:300

*December 1, 2016*

**math**

If it takes x hours, then 1/2 + 1/3 = 1/x

*December 1, 2016*

**math seventh grade**

well 550 = 5.5 * 100 so, it will take 100 minutes.

*December 1, 2016*

**Math**

sure, as long as you provide some work on your part. We don't like homework dumps here.

*December 1, 2016*

**Math**

7*18 + 4*14 + 26

*December 1, 2016*

**math**

3x-14 = 8 I suspect a typo. Is it reasonable for a kid to be almost 3 times as old as his grandfather?

*December 1, 2016*

**Math**

30/2.5 = 12

*December 1, 2016*

**Algebra**

4(6+x) = 6+x

*December 1, 2016*

**Algebra**

To fill the whole tank in x hours, 1/5 - 1/7 = 1/x but you only have to fill 1/3, so adjust accordingly.

*December 1, 2016*

**steve plz help me on my math**

just the reverse. The distributive property states that a(b+c) = ab + ac combining stuff inside the parentheses first does not involve the property.

*December 1, 2016*

**math**

huh. They gave you the formula, as well as the numbers. Just evaluate 1000 e^(-.028*50)

*December 1, 2016*

**algebra 2**

a=10 d=15 S6 = 6/2 (2a+5d)

*December 1, 2016*

**maths**

98*3 + x = 100*4

*December 1, 2016*

**math algebra**

just find t where 70*0.62^t = 10 .62^t = 1/7 t log.62 = log 1/7 t = log(1/7)/log(.62) = 4.07

*December 1, 2016*

**Math adding fractions with distributive property**

same as with any other distributive property problem: with: 6(1/2+2/3+3/4) 6(1/2) + 6(2/3) + 6(3/4) 3 + 4 + 4 1/2 11 1/2 without: 6(1/2+2/3+3/4) 6(6/12 + 8/12 + 9/12) 6(21/12) 21/2 11 1/2

*December 1, 2016*

**math**

If c is the hypotenuse, then a^2 + b^2 = 20 a^2+1=20 a = ?19 If not, then a^2 = b^2+c^2 = 1+20 = 21 a = ?21

*December 1, 2016*

**maths**

google alternating harmonic series = log(2) for many proofs and discussions, on different levels of math skills.

*December 1, 2016*

**Math**

for a square of side s, the diagonal is s?2 So, you have s?2 = 10 ...

*December 1, 2016*

**Are All Right? Math**

all are correct.

*December 1, 2016*

**MATH**

The area is a circle plus a cylinder, which can be thought of as a rectangle which has been rolled up.

*December 1, 2016*

**Health**

Sometimes a patient needs additional care that his or her regular physician cannot provide. In this instance, the physician can make a referral for a patient to see another physician. What are the three types of referrals? (1 point) regular, urgent, fast normal, fast, STAT ...

*December 1, 2016*

**maths plz help**

Whatever you copied and pasted from mangled the special characters. Try spelling out special stuff, such as sqrt() etc.

*December 1, 2016*

**Math integer**

-2(3 + -4 + -8 + 7) -2(-1 + -8 + 7) -2(-9 + 7) -2(-2) 4 -2(3 + -4 + -8 + 7) -2(3) + -2(-4) + -2(-8) + -2(7) -6 + 8 + 16 - 14 4 34 = -2(-17) so I'd be interested in how you got -17 from what's inside the parentheses.

*December 1, 2016*

**algebra 1**

f(m) = 12 - m/25

*December 1, 2016*

**Math**

If the average of the 21 students is x, then 21x + 78 + 93 = 23*75

*December 1, 2016*

**Integral Calculus**

since pi/4 = arctan(1) just plug in x=1 into the power series. That gives the actual series.

*December 1, 2016*

**Algebra**

1,2 ok 50 is 62.5% of 80

*December 1, 2016*

**Math check my answers**

all correct.

*December 1, 2016*

**Algebra**

product, not sum better review what that means.

*December 1, 2016*

**Algebra 2**

Having n in the index and in the expression is bogus. If you mean n-1 ? (3k-2) k=1 Then that can be split up into ?3k - ?2 Now, ?2 is 2(n-1) ?3k = 3?k You know that n ?k = n(n+1)/2 k=1 So for you example, 3?k = 3(n-1)(n)/2 The final sum is thus 2(n-1) + 3(n-1)(n)/2 If I ...

*December 1, 2016*

**Math**

x values change sign. y stays the same try experimenting with this -- it should be quite clear.

*December 1, 2016*

**Calculus**

(a) is correct (b) solve for t when h=0 (c) use the above t to get v

*December 1, 2016*

**Gk**

sounds like a cheap pair of glasses...

*December 1, 2016*

**Math**

524 - 520

*December 1, 2016*

**calculus**

g has a critical value where g'=0: x = ±4 max/concave down if g" < 0 g" = (x^2-4x+16)/(x-2)^2 For the tangent line, you have a point (3,4) and a slope (-7), so the line is y-4 = -7(x-3)

*December 1, 2016*

**Math**

23 years before Columbus set sail. or, maybe 11 14 16 19 ...

*December 1, 2016*

**Math**

You now have expressions for AN and NC Using the law of cosines, AN^2 = CN^2 + 2^2 - 2*CN*2 cos?ACN

*December 1, 2016*

**Math**

an angle is in degrees, not feet. Your height h is found via h/80 = tan70°

*December 1, 2016*

**math**

surely you can tell which is the greatest odd digit. Just take it from there.

*December 1, 2016*

**Algebra**

Fix the typo Then just expand and subtract, knowing that (x-4)^2 = x^2-8x+16

*November 30, 2016*

**Algebra**

w(3w-2) = 60 solve for w, then get length

*November 30, 2016*

**Calculus**

just find c such that 3c^2 = (65-9)/(4-2)

*November 30, 2016*

**Algebra 1**

double the 1st equation and you have 6x + 2y = -22 6x - 2y = -2 Now you can add them to eliminate y, or subtract to eliminate x.

*November 30, 2016*

**Math**

g = b+12 b/(b+g) = 35/100 ...

*November 30, 2016*

**calc**

since C = 2?r, dC/dt = 2? dr/dt Since dC/dt = ?/4, dr/dt = (?/4)/(2?) = 1/8 cm/min v = ?r^2h dv/dt = 2?rh dr/dt + ?r^2 dh/dt = 2?*4*12*(1/8) + ?*16*(1/2) = 20? cm^3/min

*November 30, 2016*

**Pre-Calculus**

r can be anything. So, the equation is just a straight line at that angle. tan? = -?3 y/x = -?3 ...

*November 30, 2016*

**Math**

add up the value of all the coins: 5n + 10(n+15) = 255

*November 30, 2016*

**Math -Calculus**

you need to do a definite integral. So, what are the limits? The curve intersects the x-axis at x = ±?(3/2) so now all you have to do is evaluate 6x - 4/3 x^3 at those points. Due to symmetry, you can just take twice the value from 0 to ?(3/2) f(?(3/2)) = 6?(3/2) - 4/3...

*November 30, 2016*

**Algebra**

If he makes x more cheese sandwiches, then (12+20+4+x) = 5(4+x) x = 4 check: 4+4=8 cheese out of 40 total. You can try other settings as well.

*November 30, 2016*

**Math (Geometry)**

well, if x is the number of hours worked, and y is the pay, y = 320 if x <= 40 8x if x > 40 It's a piecewise function, since it changes at x=40 hours

*November 30, 2016*

**Algebra**

no question. But there will be a guaranteed pay of 8*40 = $320

*November 30, 2016*

**Math**

If x>0, 4x > 5*2 x > 5/2 If x<0, 4x < 5*2 x < 5/2 But x<0, so x < 0 < 5/2 is a solution. Naturally, since if x<0, 2/x < 0, so 4/5 > 2/x for any negative x.

*November 30, 2016*

**6th grade math**

well, 30 = 6*5, so five times as far.

*November 30, 2016*

**Algebra**

from the axis and vertex, we know y = a(x+2) - 6 Now use the point to solve for a. You already know that a is positive (why?)

*November 30, 2016*

**Pre-Calculus**

C depending on how the equations are set up. Position involves x and y, and both depend on the time t.

*November 30, 2016*

**Math - Aglebra One (Ratios)**

If there are d dollars and h halves, then what do we know? d = h+133 d/h = 5/2 Now you can easily find h and d.

*November 30, 2016*

**precalculus**

man, this has been an agonizingly slow homework dump. Absolutely no work shown on your part, and general questions that indicate a total lack of preparation or study.

*November 30, 2016*

**College alegbra**

If the field has length x and width y, then xy = 1500 y = 1500/x p = 2x+3y = 2x + 4500/x See what you can do with that.

*November 30, 2016*

**Super Hard Math**

2*9 + 5*9 = (2+5)*9 = 7*9 did you actually try using some arrays?

*November 30, 2016*

**Math**

the height difference is 15 ft. So, now just use the Pythagorean Theorem for a triangle with legs of 15 and 36 Hint: Recall that one of your standard right triangles is 5-12-13

*November 30, 2016*

**Calculus**

exponentials grow and decay faster than polynomials. So, b,d -> 0 logs grow more slowly than polynomials, so c -> 0 a does not go to zero, since f(x)g(x) = 2x^2 + x/5 e^-x -> 2x^2

*November 30, 2016*

**Math**

so, if x is the number, what is one half of the number ?

*November 30, 2016*

**Calculus**

if you google MVT you will see diagrams of what it means. All it amounts to is that if the conditions are met, there will be one or more places in the interval where the tangent line is parallel to the line joining the points at the ends of the interval. In this case, the line...

*November 30, 2016*

**math**

with a little practice, which you evidently have, you can just read it from the equation, since b^0 = 1 for any nonzero b. But, when the function is a little more complicated, you may have to plug in t=0 and evaluate a more involved expression. Read about Newton's law of ...

*November 30, 2016*

**Math**

no. A is -6-24

*November 30, 2016*

**geometry**

6 * 8 * sin45°

*November 30, 2016*

**Math**

y=kx so, y/x = k is constant. You want y such that y/9 = 15/5 You don't really need to know what k is.

*November 30, 2016*

**math**

well, 2+3+4 = 9

*November 30, 2016*

**Math**

difference, not product

*November 30, 2016*

**math**

T-C = ((40-4t)-(-10+45t),(20+75t)-(40+70t)) = (50-49t,-20+5t) at t=0, then d=|T-C| = ?(50^2+20^2) = ?2900 = 53.9 d^2 = (50-49t)^2 + (-20+5t)^2 = 2426t^2 - 5100t + 2900 Not sure how you got your expression

*November 30, 2016*

**precalculus**

Your answer gives x = -1 y = -3/2 z = 1 but these do not satisfy the original equations. I already gave you a url which shows the row-echelon details.

*November 30, 2016*

**pre calculus**

the equation fits. Could you not do as I did, and just plug in t=1,2,3 to see that the result is as desired?

*November 30, 2016*

**Maths**

AC = AB+BC = 3+4 = 7 AC/CD = 2/1, so CD = 7/2 AD = AC+CD, so BC/AD = 4/(7 + 7/2) = 8/21

*November 30, 2016*

**Algebra**

The nth row, Rn = 41-4(n-1) = 45-4n So, there are 11 rows, since 45-48 < 0 You have an AP with a = 41 d = -4 S11 = 11/2 (2*41 + 10(-4)) = 231

*November 30, 2016*

**Algebra**

This is easy if you just break it up: 8 ?(-1)^k + 1.5k 1 = ?(-1)^k + ?1.5k The first sum is -1+1-1+1... = 0, so = ?1.5k = 1.5 ?k Now you know that n ?k = n(n+1)/2 1 so, your sum is just 1.5* 8*9/2 = 54

*November 30, 2016*

**Calculus 1**

the area of the water's surface is 4? m^2 since volume = area * thickness, the thickness is changing by 2/(4?) = 1/(2?) m/min

*November 30, 2016*

**college**

it must show all debits and credits, and they must all add up to the same value.

*November 30, 2016*

**Calculus MATH**

it's just a step function, so just add up the areas of the rectangles with heights 0,1,2,...9 and width 0.1

*November 30, 2016*

**math**

If you mean ?54 * 3i then that is 3?6 * 3i = 9?6 i ?(54*3)i = 9?2 i

*November 30, 2016*

**college algebra**

1/x = 1/60 + 1/55 x = 660/223 So, it will take them about 28.7 minutes. Sounds right, since their times are so close, it would just about cut the time in half, working together.

*November 30, 2016*

**Calculus**

A is true, since (0,1) is an open interval. Pick any nonzero x, and the limit from both sides is just 1-x. B and D are also true. C is false, since f(0) = 0 and f(x)->1 as x->0+ f is continuous on (0,1] There is a problem with the definition. It should be f(x) = 0 if x=0...

*November 30, 2016*

**precalculus**

for the row echelon stuff, enter your data here to check your results: http://www.math.odu.edu/~bogacki/cgi-bin/lat.cgi 2-7 look ok #8 is missing data, but the equation looks typical. Must be for a flight from ground level at 64 ft/s

*November 30, 2016*

**Calculus**

a is ok, since it is differentiable on (-1,1). It has a vertical tangent, bot only at the endpoint(s). b is ok for the same reason c is ok d is real on the interval, since it's ?(x+1), so it's ok too Looks to me like they all work, since the MVT requires 1. f(x) is ...

*November 30, 2016*

**pre calculus**

enough of these. Lots have been done, and a url provided.

*November 30, 2016*

**additional mathematics**

just use the formulas you know: a+d = 15 a+3d = 23 Note that T2 and T4 differ by 2d=8.

*November 30, 2016*

**math**

If you draw the diagram, you can see that you have a right triangle with 45° angles. So, the two legs are the same length: 60km.

*November 30, 2016*

**Math**

I think they want you to approximate it with the Taylor series, which involves y", y"', etc.

*November 30, 2016*