# Posts by Steve

Total # Posts: 50,479

**maths**

If there are e erasers, p pencils, and q pens, we have 2e+4p = 240 6e+p+2q = 395 e+p+4q = 415 If A is the matrix of coefficients, then A^-1 = 1/84 (-2 16 -8) (22 -8 4) (-5 -2 22) Then you have (e p q) = (30 45 85) See here: http://www.wolframalpha.com/input/?i=inverse+%7B%7B2,...

**Science**

No ideas? Surely you have a calculator.

**Algebra2**

thank you

**Algebra2**

4x^2+4y^2=64. what are the domain and range? my answer is domain;all real numbers range;-4<=4<=4

**Math c2**

well, 3?(x^2+1) = ?(9x^2+9) = ?(3x)^2 + 9) So, it looks like a horizontal compression by a factor of 3.

**Math**

well, for usage over 50 therms, the bill for x therms is y = 67.65 + 1.1917(x-50) So, plug in your y values and solve for the x values.

**maths**

well, where is x^2-x-6 = 0? You cannot divide by zero, and the square root is not real for negative values, so ... the domain is x values where x^2-x-6 is positive.

**algebra**

Think about it like this. With 5 types of seeds, there are 5 choices for the 1st flower. For the 2nd flower, there are only 4 choices. For the 3rd flower there are 3 choices. Now you know how many ways the 3 flowers can be planted. But if all you want is the combinations, the ...

**math**

4x^2+19x-5 = (4x-1)(x+5) The roots (places where the graph crosses the x-axis) are -5 and 1/4 So, where do you think the value is negative?

**Precaculus**

(0.1 cm^3)/(4?/3 * (5*10^-3 cm)^3) = 0.1/(5.24*10^-7) = 190986 cells V(t) = 0.1 * 2^(t/20)

**maths**

you know the circumference of a circle is ?d, right? Think of the circle as a round piece of string. Cut it and lay it out straight. That's how far the wheel travels in one complete turn.

**Math**

sum means add (product means multiply) same mistake. "/" means divide -8n ok your answers are ok if you meant x+(-3) times means multiply. You really seem to have a problem here... and yet you got y-5 correct.

**Math**

2(80+x) = 410 area = 80x

**Math**

well, he spent 1/4 + 1/3 + 1/5 = 47/60

**English**

clearly, neither. It just mentions shoes of no specific kind.

**Math**

5P2 * 12P4 = ?

**Algebra 2**

or, for a more condensed presentation, type in your coefficients here and see all the details. http://www.gregthatcher.com/Mathematics/GaussJordan.aspx

**Math**

they must be flying in the same vertical plane, if they are traveling with an angle relative to the horizontal ... Also, I suspect A's speed is 100?3 m/s, not mi/s. Using the law of cosines, 500^2 + (100?3 t)^2 - 2(500)(100?3 t)(?3/2) = (100?3 t)^2 They will crash in 5/3 ...

**science**

well, how many moles of Fe2O3 in 108kg? Now balance the equation: Fe2O3 + 3CO -> 2Fe + 3CO2 Now you can see how much CO is used.

**Math**

well, 27+28 = 55

**calculus**

the 3-foot radius and 2-foot depth means that y = 2/9 x^2 The arc length of the parabola is ?[0,3] ?(1+y'^2) dx Now just rotate that, remembering that the circumference of a circle is 2?r.

**Math**

well, what about zero factors?

**math**

2(w + w+9) = 110

**ATI TEAS 6 practice**

as for the -20x+20, 5(x-2)^2 = 5(x^2-4x+4) = 5x^2-20x+20

**ATI TEAS 6 practice**

not much factoring here. 5(x-2)^2 = 125 (x-2)^2 = 25 x-2 = ±5 x-2 = +5: x = 7 x-2 = -5: x = -3

**Math age problem/ Solving Multi step Equations**

a = 2m-15 a+m = 12 ...

**Calculus Answer Check**

good numbers, but what about [0,10]?

**Math**

*sigh* 7 5/16 + 3 3/4 = 7 5/16 + 3 12/16 = 7+3 + 5/16+12/16 = 10 17/16 = 11 1/16 clearly you need to review operations with fractions.

**Math**

7 5/16 + 3 3/4 place fractions over a common denominator and add.

**math**

42

**Hot math questions**

not if S is the number of shoes in S/2 pairs ...

**Maths trigonometry**

trés simple -- x = Sin Alfa / (335sin59) now just get out your calculator. sure looks like a Law of Sines problem to me.

**FUR. MATHS**

judging from the student's alleged name, we want something like (f?g)(x) = f(g) = 2g-1 = 2(5-2x)-1 = ...

**Algebra math 150**

I guess it depends on what you are trying to do...

**maths**

The range of f^-1(x) is (-9/4,?) x = (1-5y)/(2y) 2xy = 1-5y y = 1/(2x+5) so, f(x) = 1/(2x+5) domain is (-9/4,?)

**Math**

?[1,5] (ln2x - lnx) dx = ?[1,5] ln2+lnx-lnx dx = ?[1,5] ln2 dx = 4ln2

**Geometry**

Hard to say what you did wrong, since you didn't show your work. First, learn to use parentheses: 9/(4x-2) = 12/(3x+2) 9(3x+2) = 12(4x-2) 27x+18 = 48x-24 21x = 42 x = 2

**Long Division**

SEE ALL THE DETAILS HERE: http://calc101.com/webMathematica/long-divide.jsp

**math**

if you say so. Hard to tell, since you don't say when you leave...

**calculus**

Each shell has thickness dy and height x = 2/y So, the volume v is v = ?[2,4] 2?rh = ?[2,4] 2?y(2/y) dy = ?[2,4] 4? dy = 8? As a check, you can use discs, getting v = ?(4^2-2^2)(1/2) + ?[1/2,1] ?(R^2-r^2) dx where R=y and r=2 v = 6? + ?[1/2,1] ?((2/x)^2-2^2) dx v = 6?+2? = 8?

**math question**

so, move left-right 1 and up-down 2 or left-right 2 and up-down 1. One such point will be (1+1,2+2) = (2,4) I think you will find 8 such points, not 4.

**maths**

I can't figure out what circle (O, OP ) is passing from A means.

**maths**

I assume that "circle (P,12)" means a circle with center at P and radius 12. If so, then the distance between the circles is 25-12-5 = 8 Draw the diagram. Label O the point midway between the circles. Then we have two right triangles PAO and QBO PO=16 and PA=12 QO=9 ...

**Geometry**

surely you know that the circumference of the semi-circle is 300? so, add that to the 3 straight sides,

**math NEED HELP ASAP**

.60x + 1.00(120-x) = .70*120

**Calculus**

either 5+2/x < 1 or -(5+2/x) < 1 In the first case, x is in (-1/2,0) In the 2nd case, x>0 or x < -1/3 . . .

**Math**

so, just solve for d when -0.02d^2+2.6d-66.5 = 0

**Math**

#1 y = (3/4)x+b 7 = (3/4)*4+b b=4 so, y = (3/4)x+4 Clearly (0,0) does not satisfy that equation #2 x/y can be zero if x=0 Only y cannot be zero. #3 ok #4 volume is always in cubic units. Area is square units. #5 85+92+80+90+x = 5*89 x = 98 How could you possibly believe such a...

**math**

do the () first 10-7=3 3 squared=9 4 times 9 =36 36 times 7 =252 252+4=256

**math**

subtract the 25 from 14

**math**

15+19=34 34-6=28 28/2=14 14-25=negative 11

**Algebra2**

thank you very much

**Algebra2**

find a quadratic function in standard form for each set of points. (-1,2),(0,1),(1,-4)

**mathemadics**

come on. Take a stick and break it into thirds. How many pieces are there?

**math**

at 3 m/s, time t: 3t time t+1: 3(t+1) = 3t+3

**Math**

coconut: (3/5)(1/3) = 1/5 angel: (2/5)(1/6) = 1/15 assuming no cakes are coconut ... If all the cakes are either coconut or angel food, then coconut: (3/5)(1/3) + (2/5)(5/6) = 8/15

**Algebra**

how about 7*2*9 ?

**Algebra**

2 legs per animal yields 26 legs There are 6 extra legs, so what does that say? Think about what happens when you replace a chicken with a sheep.

**Calculus**

Too bad you didn't show your work... f' = 1 + 2cosx f'=0 when cosx = -1/2 x = 2?/3, 4?/3 f" = -2sinx f"(2?/3) < 0, so that is a maximum f"(4?/3) > 0, so that is a minimum See the graph at http://www.wolframalpha.com/input/?i=x%2B2sinx,+for+x+%...

**Math**

m = kh now plug in your numbers

**Math**

a:b = 3:8 b:c = 1:6 = 8:48 a:b:c = 3:8:48 a:c = 3:48 = 1:16

**Math**

no idea what the shaded region is.

**Algebra**

plot each line and the solution is where they intersect.

**math 73**

add up the amount of fat in the milk and cream. It must equal the amount in the mix. If there are x gallons of cream, then the rest (20-x) is milk. So, .22x + .02(20-x) = .04(20)

**Geometry**

2(w+78) = 260

**maths curve need help**

First step: draw the graphs! They intersect at (0,0) and (1,1). You want to rotate a small lens-shaped area. To find the volume, you can do two methods. Think of the volume as a stack of discs with holes (washers). The holes are there because a slice of area is rotated around ...

**Math**

#1 #2 are ok the volumes are in the cube of the linear ratio. So, v' = (10/15)^3 v = 8/27 v = 160 This is due to the fact that each dimension scales the same way. In the case of the sphere, replace r by (2/3)r in the formula. Then you get v = 4?/3 r^3 v' = 4?/3 (2/3 r...

**Algebra2**

a = a1 = 2*1-3 = -1 d = an+1-an = (2(n+1)-3)-(2n-3)) = 2 Now just use your sum formula S10 = 10/2 (2a+9d)

**Algebra2**

What is the sum of the first 10 terms of the sequence defined by an = 2n - 3?

**Math**

good start, but 16 years means 32 payments.

**physics**

recall that the index n is defined by n = c/v

**Calculus**

I assume a triangular cross-section. So, the width of the water surface when it has a depth of y is y/2. Thus the volume of water of depth y is v = (1/2)(y)(y/2)(8) = 2y^2 dv/dt = 4y dy/dt Now just plug in your numbers

**math**

same as for any regular n-gon: area = 1/2 perimeter * apothem But it will be very close the the circle.

**Trig**

well, (u-3)(u+1)/(u+1) = u-3 as long as u ? -1

**Algebra**

yes

**Algebra**

don't you recognize 8^2 and 9^2 ?

**Maths**

2(5x+3x) = 128 x = 8 so, ...

**Algebra**

well, 32 = 2^5 that should help

**Calculus**

e^(ax) = e^(a/b * bx) = (e^(a/b))^(bx) C = e^(a/b)

**Geometry**

42

**Calculus**

If I read all those words correctly, you mean ?[-3,3] f(x) dx where f(x) = f1: ?(4-?(x+1)) for -3 <= x <= 1 f2: |x-2|-1 for 1<x<3 Unfortunately, for x < -1 the first piece is complex, not real. Anyway, fix the presumed typo and just plug in the pieces ?[-3,1] f1...

**math**

Draw the figure. If the height is h, then you have a 40-by-h rectangle in the center, with extra lengths of x and 25-x on the longer base. x^2+h^2 = 56^2 (25-x)^2+h^2 = 39^2 x^2-56^2 = (25-x)^2 - 39^2 x = 224/5 so, h^2 = 56^2-x^2 = 28224/25 h = 168/5 so, the area is (40+65)/2...

**Math/Calculus**

Consider the set of nested shells of thickness dy. v = ?[0,4] 2?rh dy where r=y and h=218-x = (y+2)^3+2 v = ?[0,4] 2?y(218-((y+2)^3+2)) dy = 8192?/5 as a check, using discs of thickness dx, v = ?[10,218] ?r^2 dx where r=y=(x-2)^(1/3)-2 v = ?[10,218] ?((x-2)^(1/3)-2)^2 dx = ...

**Calculus**

assuming you mean 1<=x<=5, we have, using discs, v = ?[1,5] ?(R^2-r^2) dx where R=x^(1/5) and r=(x/5)^2

**Calculus**

each triangle at a distance x from (0,0) has a base of 2y = 2?(64-x^2) So, the total volume, taking advantage of symmetry is v = 2?[0,8] bh/2 dx = 2?[0,8] 2?(64-x^2)*2?(64-x^2)/2 dx = 4?[0,8] (64-x^2) dx = 4096/3

**Calculus**

Find the volume of the solid whose base is the circle x^2+y^2=64 and the cross sections perpendicular to the x-axis are triangles whose height and base are equal. Find the area of the vertical cross section A at the level x=7.

**calculus**

h^2 = 6^2 + x^2 h dh/dt = x dx/dt when h=10, x=8, so just plug in the numbers 10 dh/dt = 8*2 dh/dt = 8/5 m/s

**math**

The only way I can make sense of what you wrote is to interpret it as p = mq^3 q = nr^2 p = m(nr^2)^3 = mn^3 r^6 = kr^k p varies directly as the 6th power of r.

**Calculus AP Exam review explanation pls**

#1. Recall that the average value is 1/? ?[-?,0] 3^cos(x) dx use your calculator to find that the integral is 4.16348 Divide that by ? and you get 1.32528 #2 is just another integral. Just as distance is ? v(t) dt, here the total change in momentum is ? cost dt since ? p = F ?...

**Algebra 2**

correct

**math**

35/60 of the circumference of a complete circle of radius 6 cm.

**math**

The distance between pencil centers on each side is 1 diameter, or 7mm. At each corner there is a quarter-circle, so the entire length is 4*7 + ?*7 = 7(4+?) mm

**math**

Draw the diagram, with two congruent triangles at the ends. Notice that the two right triangles are 6-8-10.

**science**

that means that 90% remains, so (1/2)^(t/1590) = 9/10 t = 241.7 years

**maths**

h/4 = tan45°

**math**

(2(3x+100)+100)/4 - x/2 = ?

**math**

x/y = a/b (x+y)/y = x/y + 1 = a/b + 1 = (a+b)/b the rest follows

**math**

let's say that for each ounce of 5-cent rice, you buy k ounces of 6-cent rice. 7(1+k) = (5+6k)(6/5) k = 5

**calculus**

h' = 3/20 ?x the length of cable is s = 2?[0,20] ?(1+h'^2) dx = 2?[0,20] ?(1+9x/400) dx = 44.2 ft Now figure the weight.