# 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.