Friday

April 25, 2014

April 25, 2014

Total # Posts: 1,492

**math correct or not correct**

right~! :)

**chemistry **

simplified energy balance: Q,absorbed + Q,lost = 0 , or Q,absorbed = -Q,lost where Q = m*c(Tf - Ti) in which Q=heat in J, m=mass in kg, c=specific heat capacity (which has a definite value for various substances) in J/(kg*C), T=temperature in Kelvin *Tf=final temp (the same fo...

**math **

Right~! :) qt/day is fine. no need to write 1.

**math **

since 1440 is a whole number, you can rewrite it as 1440 = 1440/1 *any whole number divided by 1 is itself. then multiply fractions like normal multiplication,, numerator: number above the line, denominator: number below the line, numerator times numerator, and denominator tim...

**math **

right, 24*60 = 1440 then 1440 * 5/8 = ?

**math **

recall these conversions: 1 qt = 32 fl oz 1 day = 24 hours = 24*60 minutes using dimensional analysis to cancel units: (20 oz)*(1 qt/32 oz) = 20/32 = 5/8 qt (1/1 min)*(24*60 min/1 day) = 24*60/day now multiply them (units in qt/day): (5/8)*(24*60) how do you multiply fractions...

**Math **

True. it's actually a theorem.

**Calculus**

is that ln (x^2) or (ln x)^2 ? anyway, in any case, it is not differentiable at x = 0 because if you get the derivative, for ln (x^2): ln (x^2) = 2*ln x derivative of 2*ln x = 2/x for (ln x)^2: derivative (ln x)^2 = 2*(ln x)/x if you substitute x=0 to the derivative, the answe...

**physics**

acceleration is change in velocity over time, or: a = (v - v0)/t where v = final velocity in m/s v0 = initial velocity in m/s t = time in s assuming that it is initially at rest, v0 = 0,, the final velocity, v, is the speed of light, which is approximately 3.0 x 10^8 m/s subst...

**physics**

first, recall formula for Force: F = ma where m = mass in kg, and a = acceleration in m/(s^2) then also recall the formula for acceleration,, acceleration is change in velocity over time, thus: a = (v - v0)/t where v = final velocity in m/s v0 = initial velocity in m/s t = tim...

**physics**

acceleration is change in velocity over time, or: a = (v - v0)/t where v = final velocity in m/s v0 = initial velocity in m/s t = time in s assuming that it is initially at rest, v0 = 0,, the final velocity, v, is the speed of light, which is approximately 3.0 x 10^8 m/s subst...

**physics**

first, recall formula for Force: F = ma where m = mass in kg, and a = acceleration in m/(s^2) then also recall the formula for acceleration,, acceleration is change in velocity over time, thus: a = (v - v0)/t where v = final velocity in m/s v0 = initial velocity in m/s t = tim...

**math **

where is a and b? and is the "t" in the equations plus or another variable?

**algebra**

you're welcome, Jordyn! :)

**algebra**

(36x^2 - 49y^2)/(6x + 7y) notice that the numerator is a difference of two squares,, recall: a^2 - b^2 = (a+b)(a-b) thus the numerator can be factored into: (6x+7y)(6x-7y)/(6x+7y) then cancel the common factor and you get 6x - 7y hope this helps.

**math**

recall these conversions: 1 qt = 32 fl oz 1 day = 24 hours = 24*60 minutes using dimensional analysis to cancel units: (20 oz)*(1 qt/32 oz) = 20/32 = 5/8 qt (1/1 min)*(24*60 min/1 day) = 24*60/day now multiply them (units in qt/day): (5/8)*(24*60) = ? hope this helps.

**math**

no,, check again your multiplication.

**math**

recall these conversions: 1 qt = 32 fl oz 1 day = 24 hours = 24*60 minutes using dimensional analysis to cancel units: (20 oz)*(1 qt/32 oz) = 20/32 = 5/8 qt (1/1 min)*(24*60 min/1 day) = 24*60/day now multiply them (units in qt/day): (5/8)*(24*60) = ? hope this helps.

**math**

recall these conversions: 1 qt = 32 fl oz 1 day = 24 hours = 24*60 minutes using dimensional analysis to cancel units: (20 oz)*(1 qt/32 oz) = 20/32 = 5/8 qt (1/1 min)*(24*60 min/1 day) = 24*60/day now multiply them (units in qt/day): (5/8)*(24*60) = ? hope this helps.

**Calculus**

is that the derivative? if it is, ln(1/x) can be written as: ln (x^-1) = -ln(x) since the derivative of ln (x) is 1/x, then derivative of -ln(x) = ln(1/x)= -1/x hope this helps.

**Find the limit**

first, we observe what happens when t approaches 5: lim (t+2)/(t-5) as t->5 7/0 = infinity which can be (+) or (-) infinity since it's 5- or to the left of 5, some of the values can be 4.99, 4.999, 4.9999,, if we choose for instance, 4.999, 4.999 - 5 = -0.001 *negative*...

**chemistry**

punctuation? ...or do you mean units? molar mass can be in g/mol or lb/lbmol... they can be found in periodic table of elements.

**maths **

alright then. if using L'hopital's Rule is not allowed, then recall the property: lim (sin x)/x = 1 as x->0 therefore, lim [sin(x-1)]/(x^2 + x - 2) we can factor the denominator: (x^2 + x - 2) = (x-1)(x+2) we can then re-write the limit as: lim [sin(x-1)]/[(x-1)(x+2...

**maths **

is the function, like this: [sin(x-1)]/(x^2 + x - 2) or this: sin [(x-1)/(x^2 + x - 2)] ?

**chem/math**

take the ln of both sides: ln [4.58*10^-15] = ln [e^(Ea/2537.02)] *since ln has a base of e, the term at the right side becomes: ln [4.58*10^-15] = (Ea/2537.02) now you solve for Ea. :)

**exponents math**

exponents means to multiply by itself,, thus: (A) (-1)^3 = (-1)(-1)(-1) = ? *solve for this. (B) here, only 1 is raised by 3,, the negative sign (or the -1) is excluded: -(1)^3 = -(1)(1)(1) = ? (C) process is same as that of letter (A) (D) process is same as that of letter (B)...

**math**

first look for the least common denominator (LCD) of the denominators (4, 3 and 6) LCD = 12 now multiply this 12 to all terms to have whole numbers and coefficients: 12*(x/4 + 2x/3 + x/6) = 12*(1/2) 3x + 8x + 2x = 6 13x = 6 solve for x by dividing 6 by 13.

**science**

is 5.20x10^-3 in moles? combustion of methane (CH4): CH4 + O2 --> H2O + CO2 *combustion reaction: products are usually water and carbon dioxide balance this equation first, then use stoichiometric ratios (the ratio of the moles of CH4 and CO2), to find number of moles of ca...

**maths **

i interpreted this in two ways: first, lim [sin(x-1)]/(x^2 + x - 2) as x->1 *since, there is no common factor between numerator and denominator, it's in simplest form,, also you substitute 1 to both [sin(x-1)] and (x^2 + x - 2): sin(x-1) = sin (1-1) = 0 (x^2 + x - 2) = ...

**Math**

first, represent unknowns with variables: let x = number of hours she worked for monday-friday let y = number of hours she worked for saturday set up equation according to conditions given: (1) x + y = 42 (2) 6x + 9y = 273 there are many ways to solve for this,, if we use subs...

**Math**

represent unknowns using variables: let x = length of a side of equilateral triangle let x+10 = length of a side of square *recall that perimeter of any polygon is the sum of the lengths of its sides,, since square has 4 sides with equal lengths, and equilateral triangle has 3...

**algebra**

first, represent unknowns using variables: let x = price of hamburger let y = price of hotdogs set up equation: (1) 6x + 3y = 27 (2) 5x + y = 18.75 there are several ways to solve this,, but id we use substitution method,, choose an equation (in this case, equation (2)),, then...

**Calculus**

y' = (-1)/{[(x-3)^(3/2)][(x-1)^(1/2)]}

**math**

if 8 marbles are blue then 28 - 8 = 20 are green and red marbles then if we let x = the number of green marbles, then the number of red marbles is 3 times the number of green marbles, or 3*x,, and their total sum must be 20: x + 3*x = 20 combining similar terms, 4x = 20 now so...

**math**

first, represent the unknowns with variables: let x = number of shamrocks let y = number of horseshoes then set up equations according to the conditions given: (1) y/x = 11/2 (2) 5x = y - 3 there are several ways to solve this,, if we choose to solve it by substitution method,...

**college-typo**

oops, some typo: x = [-1 + i*sqrt(11)]/6 ; and x = [-1 - i*sqrt(11)]/6

**college**

since it's not factorable, we use quadratic formula: x = [-b +- sqrt(b^2 -4ac)]/(2a) where a=3, b=1, and c=1 substituting: x = [-1 +- sqrt(1^2 - 4*3*1)]/(2*3) x = [-1 +- sqrt(-11)]/6 thus x = [-1 + i*sqrt(11)]/6 ; and x = [-1 - i*sqrt(-11)]/6 *note: i = sqrt(-1) hope this ...

**calc**

**i'll just retype it to make the integration part clearer: integral 2x = [2x^(1+1)]/(1+1) = (2x^2)/2 = x^2 integral x^2 = [x^(2+1)]/(2+1) = (x^3)/3

**calc**

is y = 2x - x^2 the function given? if it is, area under the curve means the integral at these particular bounds,, first you have to recall how to integrate: for ax^n (a is constant), add 1 to the power, then this n+1 must be divided: integral (ax^n) = (a)[x^(n+1)]/(n+1) thus ...

**physics**

the formula for vertical distance is, d = (v0)*t-(1/2)g*t^2 where v0=initial velocity, t=time, and g=acceleration due to gravity, which is approximately 9.8 m/(s^2) *now since this is freefall, v0 = 0 and the formula reduces to: d = -(1/2)g*t^2 d = -(1/2)*9.8*(2.5^2) then solv...

**math**

white: 3 9 27 black: 1 4 13 notice that for the white triangle,, let n = number of terms,, if n=1 , white=3, if n=2, white=9, thus the pattern for white is white = 3^n for the black, notice that the next term would be the sum of previous values of both white and black,, for in...

**math**

V,sphere = (4/3)*pi*r^3 V,sphere = (4/3)*3.14*5^3 then solve for V. (units in inch^3)

**Math **

first solve for y,, to do this, transpose all terms without variable 'y' into the other side of equation: 35 - 5y = 0 -5y = -35 *when transposing a term, the sign becomes the opposite (thus 35 becomes -35) then divide everything by -5 to get y alone: (-5/-5)y = (-35/-5...

**Math - horizontal asymptote of f(x) (check)**

horizontal asymptote: y = 0 , as x approaches plus/minus infinity

**Math - horizontal asymptote of f(x) (check)**

oops i got it wrong horizontal asymptote occurs where the value of y is restricted,, so in the given function f(x)= y = x/(x-1)^2, what value of y is restricted?

**Math - horizontal asymptote of f(x) (check)**

horizontal asymptote occurs where the value of x is restricted,, n the given function f(x)=x/(x-1)^2, what value of x is restricted?

**5th math**

i'm very sorry, mr. Writeacher! i didn't know that, because i'm also a student. i promise not to do it again.

**5th math**

you just have to measure the lengths of the sides of the triangle you want to draw. for instance, if isosceles, choose the length of the two sides which must be equal (any length, like 3 cm or 5 cm) using your ruler, then the length of the last side must be different from the ...

**science**

first recall the density of water,, density is mass per unit volume,, the density of water is approximately 1 g/mL , therefore: d = m/V where m = mass in g, and V = volume in mL 1 = m/16 m = 16 grams so there,, :)

**Physics**

you need to first look for the latent heat of fusion (Lf) --- this is a constant, then use the formula: Q = m(Lf) where Q = heat in Joules, m = mass in grams *since it melted, it definitely absorbed/gained heat, thus Q is (+) so there,, :)

**5th grade math**

isosceles and equilateral triangles are different because, isosceles --> only two sides are of equal length, equilateral --> all three sides are equal isosceles and equilateral triangles both have three sides. (one characteristic they both have) so there,, :)

**5th math**

no, that's an octagon. a regular polygon has sides with equal lengths, and also with equal angles. :)

**Calculus 1**

first, recall chain rule, since there there is a function of x multiplied by another function of x (that is, x^7 and h(x)),, given a function f(x)=g(x)*h(x) f'(x) = g'(x)*h(x) + g(x)*h'(x) therefore, to get derivative of f(x)=x^7 *h(x), first get the derivative of ...

**Math. **

you have to divide 420 by 2 1/4,, to do this, you must first convert 2 1/4 into improper fraction: 2 1/4 = 9/4 *note that to convert mixed number into improper fraction, multiply the denominator (which is 4) by the whole number (which is 2), then add the numerator (which is 1)...

**math**

hmm, is this what you mean: since output is half of the input, output = input / 2

**math(Pre-Calculus)**

-f(x) means you just have to multiply every term by -1, like for (A) -(3x-1) = -3x + 1 try it to letter (B). :) then substitute the answers you get into the F(x).

**math(Pre-Calculus)**

is that really F(x)= (x+h)-f(x) or F(x)= f(x+h)-f(x) ? *the f(x+h)* anyway, A.) that's right. f(x+h) = 3(x+h)- 1 B.) you forgot to raise 2(x+h).. by 2.

**5th grade math**

please repost your question,, something that we can understand. or just describe the figure.

**algebra 1**

first represent unknowns with variables: let x = length of the second carpet let x+30 = length of first carpet. since Area=length*width, and they have the same area, Area = 9*(x+30) = 15*x 9(x+30) = 15x now solve for x. then substitute this to x+30 to get length of first carpe...

**math**

right~ :)

**math**

you just have to divide,, but first convert 1 3/20 to improper fraction,, let me see your work first. :)

**math**

what do you mean rule? do you have to write an equation or something?

**math**

notice that the output is half of the input. :)

**6th grade**

to get variable 'm' alone, transpose all terms not containing m to the right side of equation,, but remember to reverse the sign: 5/8 + m = 1 m = 1 - 5/8 *note that the sign of 5/8 becomes negative* then to subtract fractions, you need to convert 1 to a fraction such t...

**math**

yes! that's right~! :)

**math**

first combine similar terms,, that is, add the numerical coefficient of x (or the number before x): -3/4 + 1/4 *since they have the same denominator, you can add the numerator directly: (-3+1)/4 = -2/4 it now becomes: (-2/4)x = -6 now, we can multiply -1 to both sides to cance...

**6th grade math**

you have to divide,, for the first one, 1 divided by i/6 1 / (1/6) when you have to divide by a fraction, get first its reciprocal, that is interchange the numerator and denominator: 1/6 --> reciprocal is 6/1 then the operation now becomes multiplication: 1 / (1/6) becomes ...

**5 th grade math**

rounding off? to do this, first you have to know the places of each digit, for instance: 5,608 5 is thousands place 6 is hundreds place 0 is tens place, and 8 is ones place since in the question, round to nearest ten (which is 0), you look at the digit at the right (that is th...

**5 th grade math**

*half of 6 is 3 (hundred thousands place) *smallest odd digit is 1 (thousands place) how many digits? is it up to million? if yes, it's: 1 , 3 1 1 , 1 1 6 . 4 1

**math**

yes! that's right! :)

**math**

33/5 is right,, 12/4 is not. check it again,,

**math**

is that minus sign or equal sign? if equal sign, no it's not 5/11. alright,, convert first 2 3/4 into improper fraction,, let me see your work. :)

**math/algebra**

no. don't look for points yet. first, convert the given equation into slope-intercept form, y=mx+b,, alright i'll help you in this one: 3x+4y<12 now to solve for y, transpose 3x to the right side of equation, but the sign becomes the opposite (positive 3x becomes -3...

**math/algebra**

oh, so it's "less than or equal to" you have to change this into y = mx + b (slope-intercept form), alright to do this, transpose 3x to the right side of equation, and divide everything by 4 to get y,, let me see your answer for this first. :)

**Math 8th grade algerbra**

yes,, (V,new)/V = 27,, and ration of dimensions is 3 (because it is tripled according to problem) now, how is 27 related to 3?

**Math 8th grade algerbra**

Volume of cylinder = area of the base * height , or V = pi*(r^2)*h V,original = pi*(3^2)(10) *you solve for this. then for the new one, r,new = 3*3 = 9 h,new = 3*10 = 30 V, new = pi*(9^2)(30) you solve also for this. then compare their volumes, find: (V,new)/V so there,, hope ...

**math **

for #1, it's correct but the sign must be positive. :) for #2, it's not 5/11. please check your solution again.

**math/algebra**

you don't actually have to convert it to decimal. improper fraction or mixed number is fine, unless it is stated in the problem that you have to convert it. :)

**math/algebra**

right~! :) now, you can cancel out 2 from both since it is a common factor: -10/6 = -(2 * 5)/(2 * 3) = -5/3 so there,, :)

**math/algebra**

set 1: 2 and 5 set 2: 2 and 3 what number is common from both set?

**math/algebra**

yes! that's right! :) now, from the factors of 10 (which is 2 and 5) and factors of 6 (which is 2 and 3), what number is common?

**math/algebra**

right. 5 and 2 are the factors of 10 because 2 * 5 = 10 now, what are the factors of 6?

**math/algebra**

5 and..? what do you multiply by 5 to get 10?

**math/algebra**

hmm,, well try this one, what are the factors of 10?

**math/algebra**

look for a common factor of 10 and 6,, for example if you have 6/4, 6 and 4 have a common factor of 2, thus you can factor out 2 from both: 2*3 / 2*2 = 3/2 like that. try it to -10/6 ~ :)

**math/algebra**

then reduce -10/6 to lowest term.

**math **

for #1, it's correct but the sign must be positive. :) for #2, it's not 5/11. please check your solution again.

**math**

what do you need to do? do you have to graph -0.2x<-12 in a number line?

**math/algebra**

no,, they have INFINITE solutions,, any point that will satisfy either equations is a solution,, :)

**math/algebra**

oh sorry. what did you not understand? these two equations are coinciding,, thus, any point that satisfies the equation is a solution,, coinciding means, they overlap, they are the same,, here, try to look at the second equation: 6x+8y=10 if you simplify this by dividing every...

**math/algebra**

oh alright then. (1) 3x + 4y = 5 (2) 6x + 8y = 10 if you want to cancel out x, you need to multiply -2 to equation (1) so that if added to 6x it becomes zero: -2(3x+4y=5) becomes -6x - 8y = -10 then add this to equation (2): -6x - 8y = -10 6x + 8y = 10 oh, it turned out both x...

**math/algebra**

(1) 3x+4y=5 (2) 6x+8y=10 to solve using elimination, you have to multiply a factor into the equation so that when you add/combine them, one of the variables gets eliminated or canceled out,, here, if you want to cancel out x, what do you need to multiply to equation (1) so tha...

**Ap calculus**

is that at a=0 or x=0,, anyway, to get the derivative, do the chain rule since two different terms with x are multiplied,, to do this let g(x)=3x and h(x)=sin x thus d/dx [g(x)h(x)] = g(x)*h'(x) + g'(x)h(x) *g(x)*h'(x) = you get derivative of h(x)=sin x an multiply...

**SOLVE THE INEQUALITY **

to graph this, first convert this equation to slope-intercept form (y = mx + b),, then graph it like a normal line (imagine the inequality sign to be equal sign),, since the sign is only "greater than" (>) or "less than" (<) (not greater than or equal...

**SOLVE THE INEQUALITY **

solve for x or y? or, do you need to graph it?

**geometry**

circumference? oh you approximate pi to 22/7 and diameter is 3.5 ? therefore, you change 3.5 into mixed number, then into improper fraction, and multiply it to 22/7. so there,, :)

**calculus**

from the volume, 8 = x * x * h h = 8/(x^2) therefore, surface area = 2lw + 2lh + 2wh where l=length, w=width, h=height since it's an open box: S(x) = x^2 + 2[8/(x^2)](x) + 2[8/(x^2)](x) S(x) = x^2 + 32/x so there,, :)

**math!!!!!!! help 3**

oh sorry. alright, Jen.

**math!!!!!!! help 3**

first multiply 3/5 by 6 3/5 * 6 = 18/5 then convert 5 into fraction such that its denominator is 5: 5 = 25/5 therefore: (25-18)/5 = 7/5 or 1 2/5 gallons so there,, :)

**math**

all numbers are correct. :) the last one, 2 3/16, i think it's fine in mixed number form.

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