Confusion on a subtraction problem

  • Thread starter Thread starter sportsguy3675
  • Start date Start date
  • Tags Tags
    Confusion
AI Thread Summary
The discussion revolves around a subtraction problem involving fractions: \frac{x}{x^2-9} - \frac{1}{2x-6}. Initially, the poster believed their answer was \frac{1}{2x-6}, but a substitute teacher provided a different solution of \frac{1}{2x+6}. The correct approach involves rewriting the fractions with a common denominator and simplifying. The poster acknowledged their mistake in subtracting the numerators. Ultimately, the correct answer is confirmed as \frac{1}{2x+6}.
sportsguy3675
Messages
45
Reaction score
0
\frac{x}{x^2-9} - \frac{1}{2x-6}

When I first worked this problem I found the answer to be:
\frac{1}{2x-6}

However, in my English class we had this Vietnamese substitute who took my worksheet and did the problems on it in his head and pointed at the answer I wrote for this problem and walked away. He came back and worked it out in front of me and he got the answer:
\frac{1}{2x+6}

Which answer is correct?
 
Physics news on Phys.org
He is.

\frac{x}{(x-3)(x+3)}-\frac{1}{2(x-3)}

Bring to a common denominator and then simplify.

Daniel.
 
Whoops, I see where I went wrong. Messed up when I subtracted the numerators. :( Thanks for the clarification.
 

Thread 'Struggling to understand the concept of this question (ice cube in water optics question)'

TL;DR Summary: I came across this question from a Sri Lankan A-level textbook. Question - An ice cube with a length of 10 cm is immersed in water at 0 °C. An observer observes the ice cube from the water, and it seems to be 7.75 cm long. If the refractive index of water is 4/3, find the height of the ice cube immersed in the water. I could not understand how the apparent height of the ice cube in the water depends on the height of the ice cube immersed in the water. Does anyone have an...
View full post »
Thread 'Variable mass system : water sprayed into a moving container'

Thread 'Variable mass system : water sprayed into a moving container'

Starting with the mass considerations #m(t)# is mass of water #M_{c}# mass of container and #M(t)# mass of total system $$M(t) = M_{C} + m(t)$$ $$\Rightarrow \frac{dM(t)}{dt} = \frac{dm(t)}{dt}$$ $$P_i = Mv + u \, dm$$ $$P_f = (M + dm)(v + dv)$$ $$\Delta P = M \, dv + (v - u) \, dm$$ $$F = \frac{dP}{dt} = M \frac{dv}{dt} + (v - u) \frac{dm}{dt}$$ $$F = u \frac{dm}{dt} = \rho A u^2$$ from conservation of momentum , the cannon recoils with the same force which it applies. $$\quad \frac{dm}{dt}...
View full post »

Similar threads

This 3 mass atwood problem is confusing me
Replies
4
Views
952
Integral for work done leading to potential energy sign confusion
Replies
5
Views
2K
Minimizing the Energy of Two Conductors Very Far Apart
Replies
23
Views
2K
Force pulling on a string at an angle with a block at the other end
Replies
2
Views
1K
What is the problem with the units in this state equation of a gas?
Replies
12
Views
2K
Physics 1 Parabolic Motion Question Confusion
Replies
15
Views
1K
Morin 3.7 -- Block sliding sideways on an inclined plane
Replies
11
Views
1K
Estimating damped harmonic oscillator parameters from this plot of the oscillations
Replies
9
Views
2K
What is the mistake in calculating the magnetic field in this problem?
Replies
3
Views
2K
I Different Substitution for Solving an Integral
Replies
6
Views
2K

Hot Threads

Recent Insights

Back
Top