Boy Mow Chau's answer to There's a feeling's Secondary 4 A Maths Singapore question.
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(1) when solving equations, can cancel away constants, but do not cancel away any terms with unknowns, otherwise you will "lose" some of your possible answers.
(2) after obtaining final answers, best to check answers by putting EACH answer back into the original equation and make sure equation is satisfied.
(2) after obtaining final answers, best to check answers by putting EACH answer back into the original equation and make sure equation is satisfied.
Date Posted:
4 years ago
regarding point (1) mentioned above, lets re-phrase it slightly.
if you have an equation with ...
(something PLUS x) on one side, and
(something else PLUS x) on the other side,
you can subtract x from both sides.
however, if you have an equation with ...
(something MULTIPLY x) on one side, and
(something else MULTIPLY x) on the other side,
you should not divide by x on the two sides and cancel.
it has got to do with the possibility that x may be 0, and division by 0 is not allowed.
if you have an equation with ...
(something PLUS x) on one side, and
(something else PLUS x) on the other side,
you can subtract x from both sides.
however, if you have an equation with ...
(something MULTIPLY x) on one side, and
(something else MULTIPLY x) on the other side,
you should not divide by x on the two sides and cancel.
it has got to do with the possibility that x may be 0, and division by 0 is not allowed.
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