Post History
#2: Post edited
by
re89j
·
2022-01-30T23:11:29Z (about 2 years ago)
Probably best not to mention brand names
I just came across this problem on brilliant.org:- 4x(5−x)−12(5−x)+100=100
- I tried to solve it by subtracting 100 from each side then inferring if something minus something else equals zero then those two things must be equal.
- 4x(5−x)=12(5−x)
- Divide both sides by (5-x) and x must be 3.
- But brilliant had a different way of solving it that revealed there are two possible values for x.
- Where did I make a mistake in my approach to solving the problem?
- Is it incorrect to assume that if a minus b equals 0 then a must equal b?
- I just came across this problem on an online learning app:
- 4x(5−x)−12(5−x)+100=100
- I tried to solve it by subtracting 100 from each side then inferring if something minus something else equals zero then those two things must be equal.
- 4x(5−x)=12(5−x)
- Divide both sides by (5-x) and x must be 3.
- But brilliant had a different way of solving it that revealed there are two possible values for x.
- Where did I make a mistake in my approach to solving the problem?
- Is it incorrect to assume that if a minus b equals 0 then a must equal b?
#1: Initial revision
by
re89j
·
2022-01-30T23:10:46Z (about 2 years ago)
Missing a solution: Are A and B always equal if A-B=0
I just came across this problem on brilliant.org: 4x(5−x)−12(5−x)+100=100 I tried to solve it by subtracting 100 from each side then inferring if something minus something else equals zero then those two things must be equal. 4x(5−x)=12(5−x) Divide both sides by (5-x) and x must be 3. But brilliant had a different way of solving it that revealed there are two possible values for x. Where did I make a mistake in my approach to solving the problem? Is it incorrect to assume that if a minus b equals 0 then a must equal b?