-5x 45 solve the inequality?

Question

-5x > 45 solve the inequality?

anonymous · Answer

Divide 45 by -5, x > that quotient

anonymous · Answer

Be sure you flip the inequality symbol when dividing by a negative number.
-5x>45 
/-5   /-5
x<-9

tkhunny · Answer

Or, if you are like many people, and are annoyed by the flipping thing related to negative numbers, there is another way.

-5x > 45

Subtract 45

-5x - 45 > 0

Add 5x

-45 > 5x

Divide by POSITIVE 5

-9 > x

There.  Same answer.  Of course, it's unique, so it had better be the same answer.  And no inequality flipping.

anonymous · Answer

Hey i never knew that way , thanks . Although its not that hard to flip an inequality symbol :S

tkhunny · Answer

It isn't that hard, I agree, however:

1) Far too many errors result from forgetting to do that.  If your process contains a rather illogical step, you ARE likely to overlook it.

2) Most folks just memorize it and have no idea why it works.

anonymous · Answer

It has to be x > -9 else its a false statement so be careful when flipping the the sign

anonymous · Answer

tsk tsk you didnt flip the sign! & yes tkhunny your right about that one , never thought about it like that.

tkhunny · Answer

@cl10Greg No, it is the other way around. -5x > 45 Try x = -10 -5(-10) = 50 > 45 Try x = -8 -5(-8) = 40 < 45 -10 works, as -10 < -9 -8 doesn't work, as -8 > -9