| RYS # | Don’t do this | Do this | Why |
| 1 | (x + 5)2 = x2 + 25 | = x2 + 10x + 25 | (a + b)2 = a2 + 2ab
+ b2 exponents do not distribute over addition or subtraction |
| 2 | write
x - 3/2 when you mean |
write (x - 3)/2 or |
order of operations |
| 3 | (cannot be simplified) | same reason as #1: think of it as |
|
| 4 (calculator) | enter e3x as e^3x | enter e^(3x) | e^3x means e3x (order of operations) |
| 5*
|
3x = 12 3x/3 = 12/3 x = 4 |
do it in your head, just write: x = 4 |
you can move the multiplier 3 to the other side of the equation by making it a divisor |
| 6*
|
x + 1 = 5 -1 -1 ------------- x = 4 |
do it in your head, just write: x = 4 |
you can just move the term 1 to the other side of the equation and change its sign |
| 7 | | x + 7| + 3 = x + 10 | (cannot be simplified) | usually can’t just discard abs. value signs as if they were meaningless |
| 8 | log (a + b) = log a + log b | (cannot be simplified) | log (ab) = log a + log b can’t have it both ways! |
| 9* | (x + 2)(x + 3) = x2 + 2x + 3x + 6 |
just write answer: x2 + 4x + 6 |
for a product like this, the OI of FOIL can be combined in your head |
| 10*
|
(x + 3)2 = (x+3)(x+3) = x 2 +6x+9 | just write the answer: x2 + 6x
+ 9
|
use the formula: (a + b)2 = a2 + 2ab + b2 and do it in your head |
| 11
|
(by cancelling the x's) |
fraction cannot be simplified | can’t cancel common terms out of numerator and denominator; can cancel factors: (a b)/b = a/1 = a |
| 12 (calculator)
|
enter as x - 3/2 |
enter (x - 3)/2 | order of operations |
| 13 | equation: x2 = 9 solution: x = |
solution: x = |
|
| 14
|
-12 = 1 | -12 = -1 | order of operations. (-1) 2 = 1 |
| 15
|
subtract a + b from x as follows: x - (a + b) = x - a + b |
= x - a - b | distribute the "-" sign to all terms in (a + b) |
* not wrong, just inefficient/immature form for students doing college-level
algebra