PHP

[shamuntoha]

php interview asked few questions. i failed to answer it in 1 minute. does anyone know it?

 

Q.1 what is the x and y value ?

x+y = 3

x-y = 4

 

Q.2 what is the result?

{1, 2, 3, 4, 6}

 

[Mchl]

Q1. That's elementary math being taught to kids 8 or 9 years old.

 

 

And what's Q2 about?

[haku]

Never seen anything like question 2. I wouldn't even know what to do with it.

 

But I could do number 1 in my head.

[Mchl]

The second one is strange. It looks like part of the task is missing.

[lowrider.v.7.0]

Both questions are completely weird...........

 

Q 1 ..... in both equations the value of x and y cannot be same ?

 

If some one does get it please let me know

 

Q 2  ..Looks like a set of numbers........without any motive.........senseless completely

 

;D

[Mchl]

Q 1 ..... in both equations the value of x and y cannot be same ?

 

If some one does get it please let me know

 

Oh yes they can... come on... that's ridiculously easy.

 

 

[corbin]

php interview asked few questions. i failed to answer it in 1 minute. does anyone know it?

 

Q.1 what is the x and y value ?

x+y = 3

x-y = 4

 

Q.2 what is the result?

{1, 2, 3, 4, 6}

 

 

I've always heard Q1 called a "system of equations."  Like others have said, that one is quite easy.  Ones with 3+ variables and exponents (above 1, of course) are a bitch (not hard, just time consuming).

 

 

The basic concept is this:

 

a + b = c

b - c = e

 

If you can find the value of one of the variables in terms of the others, you can get it to something solvable:

 

b = -a + c

So: b - c = e is equiv to -a + c - c = e, so -a = b.

 

(You would of course need a constant in there before you could solve for real numbers.)

 

 

So, to solve your question 1, it would be:

 

x+y = 3

x-y = 4

 

x = -y + 3

 

-y + 3 - y = 4

-2y = 1

y = -1/2

 

x = 1/2 + 3

x = 3.5

 

 

Then, to check 3.5 + (-.5) = 3, 3.5 - (-1/2) = 4

[haku]

Or to shorten that into words:

 

Solve for either X or Y in one equation. Substitute that value in the first equation, and solve for the other one. Take the answer from that and substitute it into the original equation and solve for the first variable.

[corbin]

Eh yeah.  I just had nothing better to do... Get kinda overboard on posts sometimes ;p.

[haku]

No worries - I thought both go well in combination with each other. Some people work better with number explanations, some work better with word explanations.

 

 

[dclamp]

Q.2 what is the result?

{1, 2, 3, 4, 6}

 

result is some one who cant count to 6.

[corbin]

Whoa I just noticed something!

 

 

There's no 5.  Didn't see that before.  But still, wtf?  It's just a set of numbers.

[pyrodude]

Similar to corbin, I solved #1 by solving for 1 of the variables, except I did it by adding the equations (since the y's cancel eachother out)

 

x + y = 3

x - y = 4

 

---------

 

2x = 7

 

---------

 

x = 3.5

 

then plug the 3.5 in for x and voila.

 

It shaved a little time off for me (and/or a little paper if you were writing it out) but it would only work if one of the variables cancelled out.

[Mchl]

I've actually created main matrix for this set of equations

    | 1  1 |
W = | 1 -1 |

And also Cramer's matrices for each variable

     | 3  1 |
Wx = | 4 -1 |

     | 1  3 |
Wy = | 1  4 |

 

Then I calculated determinants for each of them

det(W) = -2 != 0

det(Wx) = -7

det(Wy) = 1

 

And calculated both variables using Cramer's rule

 

x = det(Wx)/det(W) = 3.5

y = det(Wy)/det(W) = -0.5

 

Now. Who solved this using graphical method? 

[Vermillion]

... Do they actually ask you to resolve those systems with two variables? I have been learning PHP on my own time and in school we don't know any programming languages whatsoever, so I have never taken such test.

Why do you need to take a PHP test?

[Mchl]

I suppose that when you want to hire a programmer, you wan't to hire one that knows basic maths.