# Erreix

### Differential equation: Inverse differential operator method. ?

Particular integral of

(D^2 +4)y = cos(2x) + cos (4x)

Can anyone help, I don't know what to do to the

cos (4x).

Mathematics2 days ago### Application in differential equations. ?

Can anyone help me in this problem. This is the only problem I was not able to solve in my exam. I want to know the answer pls.

Mathematics3 weeks ago### Material balance.. plz help?

It was found that 44 g oil can be extracted from 100 g copra containing 30% moisture . If the same copra is dried to 3.5% moisture , calculate the grams of dried copra that will give 2,000 g of oil.

2 AnswersEngineering3 weeks ago### Aromatic compounds' nomenclature. ?

My answer is 1-bromo-2,3-dimethylbenzene, but the answer online is 3-bromo-1,2-dimethylbenzene. Why is that?

2 AnswersChemistry4 weeks ago### Organic chemistry question (nomenclature).?

Which one is correct?

My answer is the second one. I got the first answer online. If the first answer is correct, can you explain me why ?

1 AnswerChemistry4 weeks ago### Is 4x dx + x dy = 0 a homogeneous and exact differential equation? ?

1 AnswerMathematics2 months ago### Is it possible for a degree of a homogeneous Differential equation to be negative?

eg. dy/dx = 1/(y-x)

f(tx,ty) = t^(-1) (y-x)

1 AnswerMathematics2 months ago### Solve for the integrating factor of (x+y)dx-(x-y)dy=0?

u = e^ ∫ [(∂M/∂y - ∂N/∂x)/N]dx

where M=x+y ∂M/∂y = 1

N= - (x-y) ∂N/∂x = -1

u = e^∫ [2/(y-x)] dx -----> I'm always stuck in this partwhat should I do if there's an f(x,y)? I tried using (∂N/∂x - ∂M/∂y)/M and it's still the same. Is there another method or am I just wrong?

2 AnswersMathematics2 months ago### Engineering mechanics: static equilibrium of trusses.?

So this is the Free body diagram, I am tasked to find the forces at point A and B; forces acting on the joints

can you see if my answer is correct

2 AnswersEngineering2 months ago### Org chem related question.?

I cannot understand the highlighted words-regioselectivity...can anyone explain to me? I cannot find in the internet.

1 AnswerChemistry2 months ago### I'm currently trying to answer this problem in the book. The given answer is $51.9/ton.?

Paper pulp is sold on the basis that it contains 12 percent moisture; if the moisture exceeds this value, the purchaser can deduct any charges for the excess moisture and also deduct for the freight costs of the excess moisture. A shipment of pulp became wet and was received with a moisture content of 22 percent. If the original price for the pulp was $40/ton of air dry pulp and if the freight is $1.00/100 lb shipped, what price should be paid per ton of pulp delivered?

I first converted the freight price ($1.00/100lb) into $/tons

= $22/ton

Since the excess moisture is the basis for deduction in charges, I took the difference:

22-12=%10

Afterwards, I multiplied the price for the pulp and freight to 0.10 and subtracted them to their original prices. Lastly, I added the two to get the price.

price paid per ton of pulp = [40 - (0.10 x 40)] + [22 - (0.10 x 22)] = $55.8/ton

But it seems my understanding is wrong, can you tell what am I missing or misinterpreted in the problem?

1 AnswerEconomics2 months ago### I'm converting 15.0kmol of C6H6 to mol(g-atom)C.?

I converted 15.0kmol to mol=15, 000 mol of C6H6. And for every mol of benzene, there is 6 mol of C. Now I got 90, 000 mol of C.

But I think it is missing something, the question is asking "mol(g-atom)C", clearly my answer does not have (g-atom).

What should I do here, should I multiply it by Avogadro's number? can you please explain.

2 AnswersChemistry2 months ago### I'm confused in lb-mol, can you clarify it.?

I am answering this question 15kmol to lb-mol

1) At first, I tried to convert it by using 1lb-mol = 453.59mol

2) My second attempt is to converted 15kmol to kg using its molar mass and converted kg to lb afterward.

Which one is correct? can you explain why

2 AnswersChemistry2 months ago### Can you offer some advice on how to get the density of calcium carbonate (kg/L) in this problem?(I'm not asking for answer, just a guide)?

Limestone (calcium carbonate) particles are stored in 50-L bags. The void fraction of the particulate matter is 0.30 (liter of void space per liter of total volume) and the specific gravity of solid calcium carbonate is 2.93.

a) Estimate the bulk density of the nag contents (kg CaCO3/liter of total volume) b) Estimate the weight (W) of the filled bags. State what you are neglecting in yourestimate.c) The contents of three bags are fed to a ball mill, a device something like rotating clothes dryer containing steel balls. The tumbling action of the balls crushes the limestone particles and turns them into a powder. The limestone coming out of the mill is put back into 50-L bags. Would the limestone (i) just fill three bags, (ii) fall short of filling three bags, or(iii) fill more than three bags? Briefly explain your answer.

2 AnswersHomework Help2 months ago### e^t, where t is time. Both the exponential function and its argument must be dimensionless. ?

Clearly the function has a "t" as a unit of time. How can this equation be valid. Can anyone help me understand this paradox?

3 AnswersMathematics2 months ago### Engineering mechanics: Equilibrium of Rigid bodies Problem ?

Solve for the reaction forces on A and C.

I'm kinda lost to the part involving the cable.

1 AnswerEngineering3 months ago### What makes alkyne C2H2 nucleophile?

1 AnswerChemistry3 months ago### Is (C≡N^-) compound a nucleophile or electrophile? ?

I answered nucleophile in this. My reasoning was because the molecule contains nitrogen that has a pair of lone electrons. Also, nitrogen has a greater electronegativity compared to carbon. Thus, giving it a partial negative sign.

I checked my answer on the book and it was correct. However, I'm not convinced in my explanation. If the Nitrogen atom has a partial negative sign, then carbon will have a partial positive sign. So, why is the compound only considered nucleophile?

2 AnswersChemistry3 months ago### In finding a differential equation to representing something (e.g. family of conic sections), is it necessary to use integration or not?

In the question find the DE of the family of circles of fixed radius r with centers on the x-axis, I saw the answer only containing differentials. Even the method used was only differentiation.

When I tried answering this question, "form the DE representing all tangents to the parabola y^2=2x," I used differentiation and integrated afterward. Is this wrong? Should I just differentiate and get the equation from that?

2 AnswersMathematics3 months ago### Find a solution to the boundary value problem y'' +4y = 0 ; y(π/8)=0 , y(π/6)=1, if the gen. soln. to the D.E is y(x)=C1sin(2x) + C2cos(2x) ?

I'm currently in case 1, where y(π/8) = 0.

I substituted y(π/8) = 0 to y(x)=C1sin(2x) + C2cos(2x) and got the value for constant which C1 + C2 = 0. But I can't find a way to substitute this back into the equation to get a particular solution.

Pls. help. Or hint if there is something wrong with my method.

2 AnswersMathematics3 months ago