# Sanity check

• Mar 28th 2009, 02:03 AM
Sanity check
1. If you re-arrange

$a = \frac {3 + b} {2}$

to make b the subject you get

$b = 3 - 2a$

Yes?
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2. Also, Mulitplying out

$(x + 1)(2x - 3)$

gives

$2x^2 - 3x - 3$

I'm having a slow morning, are these correct?
______________________________________
3. Sim Equations

If you have

$x + y = 4$
$3x + 5y = 22$

I make $x = -1$ and $y = 5$

Is that correct?
• Mar 28th 2009, 02:29 AM
earboth
Quote:

1. If you re-arrange

$a = \frac {3 + b} {2}$

to make b the subject you get

$b = 3 - 2a$

Yes? ........ No
_____________________________________
2. Also, Mulitplying out

$(x + 1)(2x - 3)$

gives

$2x^2 - 3x - 3$ ........ No

I'm having a slow morning, are these correct?
______________________________________
3. Sim Equations

If you have

$x + y = 4$
$3x + 5y = 22$

I make $x = -1$ and $y = 5$

Is that correct? ........ Yes

$a = \frac {3 + b} {2}~\implies~2a=3+b~\implies~2a-3=b$

$(x + 1)(2x - 3) = 2x^2-3x+2x-3 = 2x^2-x-3$