Yilin's answer to Czzz's Junior College 1 H2 Maths Singapore question.
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here u go
Date Posted:
2 years ago
sorry to advise that the answers / method are incorrect.
important concept : cannot multiply both sides of the inequality by a quantity that can either be positive or negative, because when the quantity is negative, have to change the direction of the inequality sign.
since x+3 can be positive or negative, cannot multiply by x+3.
can only multiply by a quantity which is definitely positive. in this case, multiply both sides of the inequality by (x+3)^2. further solving gives final solution as ...
-4<=x<-3 or x>=1.
note that -3 has to be excluded because it will result in division by 0.
for solving equations & inequalities, should always substitute back into original equation / inequality to check that the answer satisfies.
JC, and other students with graphics calculator, can also see the curve in the GC to check that the solution is correct.
important concept : cannot multiply both sides of the inequality by a quantity that can either be positive or negative, because when the quantity is negative, have to change the direction of the inequality sign.
since x+3 can be positive or negative, cannot multiply by x+3.
can only multiply by a quantity which is definitely positive. in this case, multiply both sides of the inequality by (x+3)^2. further solving gives final solution as ...
-4<=x<-3 or x>=1.
note that -3 has to be excluded because it will result in division by 0.
for solving equations & inequalities, should always substitute back into original equation / inequality to check that the answer satisfies.
JC, and other students with graphics calculator, can also see the curve in the GC to check that the solution is correct.
yes u are right! thanks for correcting me! i wrongly assumed that the unknowns are positive
Thanks
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