# Posts by Steve

Total # Posts: 53,644

**Math**

all correct

**Math**

LCM(5,6,8) = ? Make up your mind whether it's stamps or coins ...

**English grammer**

" i will read a book tonight"

**maths**

ok - now what?

**Science**

only plant cells have cell walls

**Xtremely Diffucult ALgebra**

M + (M-A) = B (3,7)+(3-9,7-3) = (3,7)+(-6,4) = (-3,11) -3+11 = 8

**Math**

since a,b,c,d are all nonzero (a/b) / (c/d) = a/b * d/c = ad/bc which is a rational number. There may be other items to consider, depending on what you have already established ...

**earth science**

most the economy will be effected. Plastic bag factories would be shut own and people would be out o jobs.

**Algebra**

looks good to me.

**Algebra**

So far so good. Have you tried factoring each expression, to eliminate common factors? These all appear to factor easily.

**Algebra**

Man, you need to learn about parentheses. I think you mean (x-11)/(6-x) ÷ (x^2-121)/(x-6) = -(x-11)/(x-6) ÷ (x^2-121)/(x-6) = -(x-11)/(x^2-121) = -(x-11)/((x-11)(x+11)) = -1/(x+11) The others can be done in the same way. Maybe you can show some of your work ,,,

**Geometry**

just plug in your expressions. You know that ST+TU = SU x+3 + 4x-6 = 12 5x = 15 x=3 Now you can easily find all the lengths.

**Math**

If we change bases to make all those logs base e, we have x = ln(bc)/lna y = ln(ac)/lnb z = ln(ab)/lnc x+y+z = (ln(bc)*lnb*lnc + ln(ac)*lna*lnc + ln(ab)*lna*lnb]/(lna*lnb*lnc) xyz-2 = (ln(bc)*ln(ac)*ln(ab)-2*lna*lnb*lnc)/(lna*lnb*lnc) OK. Just to make things more readable, let...

**Maths - oops**

I botched it at the end. I'm sure you can see where. Good work, Reiny, as usual!

**Maths**

S(n)-S(n-3) = 1024S(3) (a(r^n-1)-a(r^(n-3)-1)/(r-1) = 1024(r^3-1)/(r-1) (r^n-1)-(r^(n-3)-1) = 1024(r^3-1) r^(n-3)(r^3-1) = 1024(r^3-1) r^(n-3) = 1024 = 2^10 So, let's say r=2 and n=13 Then the sum of the last 3 terms is 2^11+2^12+2^13 = 2^10(2+4+8) and the sum of the 1st 3...

**algrbra**

b^2 is always positive, so since a>0, ab^2 > 0

**5th grade Math**

all ok except the last. It is already rounded to the nearest thousandth. You rounded it to the nearest hundredth!

**math**

As I said before, https://www.jiskha.com/display.cgi?id=1507264737

**Calculus II**

This is just like the one you posted earlier at https://www.jiskha.com/display.cgi?id=1507322985

**ALGEBRA**

it works better if you use <=

**Math**

72 are present, so 11 are absent 11/83 = 0.1325 = 13.25% So, B an hour is 3600 seconds, so 12 seconds is 1/300 hours 72km = 72000m 72000/300 = 240

**algebra 2**

C is correct

**Calculus II**

dp/dt = k(72-5p-(9+2p)) = k(63-7p) dp/(9-p) = 7k dt -ln(9-p) = 7kt + C 1/(9-p) = c*e^(7kt) 9-p = c e^(-7kt) p = c e^(-7kt) + 9 p(0) = 2, so c+9 = 2 c = -7 p(t) = 9 - 7e^(-7kt)

**Math**

If he pays s for internet service and c for cable, then s+c = 150 we want c such that (c-70)+2s = 150-20 c-70+2(150-c) = 130 c = 100 check: cable costs 100 internet costs 50 on the new plan, cable costs 30 internet costs 100 for a total of 130 = 150-20

**Math**

f(x) = x^2/(x^2-1) It might help to visit https://math.stackexchange.com/questions/312381/proving-prodk2-1-k2-n1-2n-by-induction to see that n ? (k^2-1)/k^2 = (n+1)/(2n) k=2 so, you want n such that 2n/(n+1) < 1.98

**Pre-Calculus**

multiply by the conjugate (2+5i)/(4-3i) * (4+3i)/(4+3i) = (2+5i)(4+3i)/(4^2+3^2) = (-7+26i)/25 = -7/25 + 26/25 i

**Math exponent & radicals**

If you mean 4^x - 4^(x-1) = 24 then If you let u = 4^(x-1) then you have 4u-u = 24 u = 8 4^(x-1) = 8 x-1 = 3/2 x = 5/2

**Math**

open

**math .**

That's better

**math**

3-1+3 = 5

**Maths**

(11/10) / (10/11) = 1.21 so, 21% gain

**math**

google is your friend. You might start here: https://math.stackexchange.com/questions/2132148/if-cosa-bcosb-ccosc-a-frac-32-prove-that-cosacosbcosc-sinas

**Math**

#1 1.6+y-1.6 = -7.3-1.6 y = -8.9 #2 (-2/3)n(-3/2) = 12(-3/2) n = -18

**Calculus**

nope. Both grow at the same rate: e^.05t The population of A is 2*B but the growth rate is the same.

**Algebra**

well, does -11 make the equation true? Coming up with an answer is only half the battle. You also need to know how to check to see whether it is correct. 5(-11)-(9(-11)-10) = -55-(-99-10) = -55-(-109) = -55+109 = 54 So, I guess you made a mistake. You could have discovered ...

**Pre-Calc**

well, 151e^(10r) = 173 e^(10r) = 173/151 r = ln(173/151) / 10 = 0.0136

**GEOMETRY**

The above instructions are rather murky at best. The key is to construct a right angle. There are lots of explanations on how to do this, such as the one at http://www.mathopenref.com/constsquare.html

**MATH**

what is 6 more than x? x+6 what is 6 less than x? x-6 so, now what do you think?

**maths**

Who cares what EC dollars are? G$60 = US$0.60

**Math (Algebra 2 / Trig)**

well, plug in your point! (-4)^2+b(-4)+7 = -9 16-4b+7 = -9 -4b = -32 b = 8 check: x^2+8x+7 = (x+4)^2-9

**math**

well, you have a+42(1/2) = 26 a+21 = 26 a = 5

**algebra**

cool

**Pre-Calc**

f-1 = 2x^3 (f-1)/2 = x^3 x = ?((f-1)/2) so, f^-1(x) = ?((x-1)/2)

**Pre-Calc**

(f/g)(x) = f(x)/g(x) = (1/x)/(x^3) = 1/x^4 clearly the domain of f/g is all reals except 0, as are the domains of f and g separately. Note, however, that (fg)(x) = x^2, whose domain is all reals, but since f and g are not defined at x=0, neither can (fg) be.

**math**

I assume the missing operators are +, and thus that you mean tan^3x/(1+tan^2x) * cot^3x/(1+cot^2x) = (1-2sin^2x cos^2x)/(sinx cosx) but that is in fact not true. Maybe you can fix it up and try again.

**Math**

well, 165 = 11*15 ...

**math, graphs**

If there are x campers and y counselors, then y = 1/4 x Now just plug in the various numbers for x. For example y(8) = 8/4 = 2 ...

**statistics**

42 and 42

**Math**

LCM(6,8) = 24

**maths (trigonometri)**

tanB = 3/4 sinB = 3/5 cosB = 4/5 (Draw a 3-4-5 right triangle to see this) Now recall your double-angle formulas: sin2B = 2 sinB cosB cos2B = cos^2B - sin^2B Now just plug in your numbers...

**math**

20 + 20m <= 100

**Physics**

with an initial speed of v, v cos40° = 1.3/1.4

**Algebra 1**

equals subtracted from equals are equal. equals divided by equals are equal. 7y+y = 7y+ny y = ny 1 = n (if y?0)

**Math**

(a) that would be the powers of 2: 1,2,4,... (b) 1024 = 2^10

**Math**

>49 ends in 0 prime factors are 2,5,? one factor is repeated: 2*5*2 = 20 -- nope 2*5*5 = 50 -- yep

**Pre-algebra**

a=7,e=5, so c+d=5 b+c=d 7+b=c b = c-7 d = 5-c b+c=d c-7 + c = 5-c 3c = 12 c=4 ...

**Math**

16*60 = 960

**Mathematics**

duh - just add up the times. for part 2, which is the greatest? 2/56 or 100/5 or 20/106 that's easy, right?

**Mathematics**

well, there are 3 1/3's in 1, right? So, since 2/3 is twice as big, there are half that many 2/3's, or 3/2 (3/2)(2/3) = 1

**math**

If the cost is c, then the price is 2c * 0.85 = 1.7c

**nats**

the radiation takes place at the surface of the sun.

**Math**

v*0.85^2 = 1445

**Math**

12500*0.93^4

**algebra**

qz = k so, you want z such that 49z = 7*15

**Math**

there's nothing to solve. Just plug in your angles and get out your calculator. cos0 = 1 cos135 = cos225 = -1/?2 Those are standard angles. You will have to adjust them to agree with your unusual notation.

**Mathematics**

just set them equal: ?r^2 = 2?r = x Now eliminate r, and you have r = x/(2?) ?(x/(2?))^2 = x ?x^2 = 4?^2x x = 4? check: 2?*(4?/2?) = 4? ?(4?/2?)^2 = 4?

**Math**

-4 7/8 = -39/8 (-39/8)(2/3) = -78/24 = -13/4 = -3 1/4

**Math**

-4 7/8 = -(4 + 7/8) so, (-4 7/8)(2/3) = -4(2/3) - (7/8)(2/3) the example shown forgets to multiply the 4 by 2/3 3 11/12 is also wrong, most clearly because it is not negative. How did you arrive at that answer? How can you possibly need assistance in showing your own work?

**Algebra 2**

remember f(x-h) shifts right by h so, you have shifted left by 7, then up by 9

**Algebra 2**

g(x) = -f(x) = ...

**Algebra 2**

compress: f(x) -> 1/4 f(x) reflect: f(x) -> -f(x) g(x) = -1/4 f(x) = 5/4 x

**algebra**

what is the normal to the plane that passes through (0,0,0)? If the distance from the plane to the origin is d, then d^2+r^2 = 17^2

**Math**

just multiply the cost per box by the number of boxes: t = 3c

**Math**

No idea what course. Sorry. Try posting a sample problem, then using the help you get to solve similar ones.

**math please help**

with what? Do you think we know your course? Try posting a sample question, then using our help to solve others like it.

**math**

stop whining under different names, and ask a question!

**math**

ab = sinx cosx + sinx cosy + cosx siny + siny cosy = sin(x+y) + sinx cosx + siny cosy using your sum/difference formulas, = sin(x+y) + 1/2 sin2x + 1/2 sin2y = sin(x+y) + sin(x+y)cos(x-y) = sin(x+y)(1+cos(x-y)) a^2+b^2 = cos^2x + 2cosx cosy + cos^2y + sin^2x + 2sinx siny + sin^...

**maths**

you asking or telling? If the latter, and you want to know how old gabe is now, then g+5 = 2(g-11+5)

**Math**

25000 * (1+.12/2)^(2*2) * (1+.10/4)^(4*2.75) = ?

**Math**

whole or integer or rational

**Math**

no. You subtract exponents, not divide. To see why, expand things out: m^8 = m*m*m*m*m*m*m*m m^4 = m*m*m*m now, when you divide, only four of the factors cancel, not six.

**Algebra 2**

f(2x) shrinks horizontally by a factor of 2 (x only has to be 1/2 as big to achieve the previous value) f(-2x) shrinks then reflects across the y-axis -f(-2x) then reflects across the x-axis -f(-2x)+5 then shifts up by 5

**college algebra**

If the chemical occupies 400 of the 1000 ml of solution, then it is a 40% solution. 25% is 5/8 as strong, so the volume of solution has to grow by a factor of 8/5, to 1600 ml.

**Math**

Vs*Ts = 88 (Vs-13)(Ts+4) = 72 22*4 = 88 9*8 = 72

**Physics**

add the two velocities in a right triangle. ?(1^2+3^2) = ?10 mi/hr 300 yds = 300/1760 = 0.17 miles so, it will take 0.17 hours to cross the river. Since the river flows 3 times as fast as he swims, he will wind up 3*0.17 = 0.51 miles downstream.

**calculus**

correct

**calculus**

yes. since 3=?3*?3, ?3/3 ?3/(?3*?3) = 1/?3

**calculus**

3cotx - ?3 = 0 3cotx = = ?3 cotx = 1/?3 Now it's time to review the "standard" angles whose trig functions are easy to remember. One of these is 60°, where cot60° = 1/?3

**Math plz help**

#2. Remember that |x| = x if x >= 0 |x| = -x if x < 0 So, you have |y+4| < 1 so, either y+4 >= 0, meaning y >= -4 or y+4 < 0, meaning y < -4 If y >= -4 y+4 < 1 y < -3 If y < -4 -(y+4) < 1 -y-4 < 1 -5 < y But also, we started with y <...

**Math plz help**

clearly not 2D. Just plug in y=2 |2+4| = |6| = 6 Bzzzt #3 is also wrong. You forgot to divide by 2. |2r| = 12, not |r| = 12 #4 is correct

**Math**

There is no unique solution. This is just the equation of an hyperbola. Some integer solutions are (-3,3) (0,-9) (1,19) (4,7) y = (10x+9)/(2x-1)

**fire dynamics**

no idea. how fast does it burn?

**fire dynamics**

1 gallon = 231 in^3. The fuel depth in the spill is volume/area: 3500*231/2500? = 102.94 in so, at 6 in/hr, it will burn for 102.94/6 = 17.157 hours

**algebra**

KE = 1/2 mv^2 2KE = mv^2 m = 2KE/v^2 C = 0.5x+10 C-10 = 0.5x x = 2C-20

**Advanced Algebra**

Bart made some home improvements for $6,091 using a six-month deferred payment plan with an interest rate of 23.79%. What is the balance after the deferment period if no payments are made? A.$6,091.00 B.$6,776.90 C.$7,540.05 D.$6,852.40 My answer is D

**Advanced Algebra**

Jeffrey earned a gross income of $51,280 last year. He made $1,746.83 in student loan interest deductions, donated $2,914 to his favorite charities and paid $3,941.47 in home mortgage interest. Jeffrey claims a standard deduction of $11,400 for himself and his non-working ...

**math**

well, only b is rational ...

**Pre-Calculus**

If x is liters and y is gallons, then y = kx k = 14/53 now plug in y=25 Or, since the ratio is always the same, and you have (25/14) as many gallons, you will have (25/14) * 53 liters

**Pre-Calculus**

w = kz so, w/z = k, a constant. So, you want w such that w/3 = 9/-6

**Pre-Calculus**

well, y=kx, so plug in the values.