+130511 -10x-8y=7
30x+24y=-20
We can quickly see that this sytem has no solution....if we multiply the first equation by -3 on both sides, we get:
30x + 24y = -21
This says that the left side = -21
But the second equation says that the same left side = -20.
And this is impossible. Adding two terms together can't produce two different answers.
Correct.
$$-10x - 8y = 7$$
$$30x + 24y = -20$$
If you rearrange the first equation you get:
$$y = \frac{7+10x}{-8}$$
Substituting that into the second equation gives you:
$$30x + 24(\frac{7+10x}{-8}) = -20$$
Expanding and simplifying the bracket gives you:
$$30x - 21 - 30x = -20$$
The two 30x terms cancel out leaving you with -21 = -20, and so the equation is unsolvable. Changing the -20 in the second equation to a -21 would make it work, however.
EDIT: actually, going back and doing it with 21 doesn't give a definite solution, since then the two equations simplify down to the exact same thing, meaning you've only really got one equation to work with.
+130511 -10x-8y=7
30x+24y=-20
We can quickly see that this sytem has no solution....if we multiply the first equation by -3 on both sides, we get:
30x + 24y = -21
This says that the left side = -21
But the second equation says that the same left side = -20.
And this is impossible. Adding two terms together can't produce two different answers.
