Straight

\((a \cdot b)^2 = 25 \mbox{ } | \mbox{ } \sqrt{} \\ a \cdot b = 5\)

because you guys had different answers, I did it myself and I found idk ( I didn't count) numbers of which 24 numbers are distinct.

1138, NO
1183, NO
1146, NO
1164, NO

1226, NO
1262, NO 
1234, --------------------------- 1
1243, --------------------------- 2

1318, NO
1381, NO
1324, ---------------------------- 3
1342, ----------------------------- 4

1416, NO
1461, NO
1423, ------------------------------ 5
1432, ------------------------------ 6

1614, NO
1641, NO
1622, NO

1813, NO
1831, NO

2126, NO
2162, NO
2134, ----------------------------- 7
2143, ----------------------------- 8

2216, NO
2261, NO
2223, NO
2232, NO

2314, -------------------------------- 9
2341, -------------------------------- 10
2322, NO

2413, -------------------------------- 11
2431, -------------------------------- 12

2612, NO
2621, NO 

3118, NO
3181, NO
3124, -------------------------------- 13
3142, --------------------------------- 14

3214, -------------------------------- 15
3241, -------------------------------- 16
3222, NO

3412, -------------------------------- 17
3421, --------------------------------- 18

3811, NO

4116, NO
4161, NO
4123, ---------------------------------- 19
4132, ------------------------------------ 20

4213, ------------------------------------- 21
4231, ------------------------------------- 22

4312, ------------------------------------ 23
4321, ------------------------------------ 24

4611, NO

6114, NO
6141, NO
6122, NO

6212, NO
6221, NO

6411, NO

8113, NO
8131, NO

8311, NO

This was just like a check that geno's answer was correct... .

thus there are 24 ways.

3x^2 + 10x + 8 =

3x^2 + 6x + 4x + 8 =

2(3x + 4) + x(3x + 4) = (3x + 4)(x + 2)

so (3x + A)(x + B) = (3x + 4)(x + 2).

4 - 2 = 2,

thus our answer is 2.

2x ( x + 10 ) = -50  | :2

x ( x + 10 ) = -25 

x^2 + 10x = -25 | + 25

x^2 + 10x + 25 = 0

Use quadratic formula:

-b ± sqrt ( b^2 - 4ac )               -10 ± sqrt ( 10^2 - 4 * 1 * 25 )       -10 ± sqrt ( 100 - 100 )     -10 ± sqrt ( 0 )          -10

------------------------------     =     --------------------------------------- =  ------------------------------  =  --------------------- =  ----------- = -5 ± 0, so:

            2a                                                 2                                             2                                       2                       2

x_1 = -5

x_2 = 5

( - 5 ) + 5 = 0.

The answer is 0.

...

Then b = -4 and c = 50.

b + c = -4 + 50 = 46

You should rather say thanks. 

Also when it's wrong or right.

1.833333...

That's wrong.

\(\frac{13}{6} = 2.1\overline6\)

n = 9

What???

\(\frac{1}{m} + \frac{1}{n} = \frac{2^2}{(mn^2)}\) whereby m and n are positive integers and \(m \neq 0\) and \(n \neq 0\).

So when m and n are positive then \(n(m + n) = 4\).

Distribute \(n^2 + nm = 4\).

There is only one solution: m = 3 and n = 1.