solve -np-9030 for n. show your work.

Question

solve -np-90>30 for n. show your  work.

anonymous · Answer

first, add 90 to both sides

anonymous · Answer

so -np>120?

anonymous · Answer

yep! now what would you divide 120 by to get (n) by itself?

anonymous · Answer

p?

anonymous · Answer

yes, but that would leave you with (-n) alone, not just (n), so it would work, but you would have to do another step to finish the problem

anonymous · Answer

so -np?

anonymous · Answer

you would divide 120 by (-p) so the negative on the left side goes away. and what happens to the inequality sign when you divide by a negative?

anonymous · Answer

it flips

anonymous · Answer

yes, so do that

anonymous · Answer

so n<120p?

anonymous · Answer

well, what did you do with the negative sign? when you flip the inequality sign, the negative sign is still in the equations, you don't get rid of it

anonymous · Answer

the p is negative, so would it be n<120-p?

anonymous · Answer

and you divide 120 by (p), you don't multiply 120 by (p)
so it would look like this:
-(120/p) 
now, knowing this, what is the full inequality solved for n?

anonymous · Answer

n<-120/p? do I have to put the parentheses?

anonymous · Answer

not really, but |dw:1388342619192:dw|if you wrote out the equation on paper it would look like this

anonymous · Answer

o ok. I think I got it. Thank you so much!

anonymous · Answer

so you have the right answer! you're welcome!

anonymous · Answer

you cannot solve this no way no how

anonymous · Answer

unless you are told that $p>0$ somewhere, you cannot divide by $p$ because you do not know if $p$ is positive or negative

anonymous · Answer

so how am I supposed to solve it?

anonymous · Answer

does it say somewhere that $p$ is a positive number?

anonymous · Answer

when solving an inequality, you can never multiply or divide by a variable, unless you know in advance what the sign of the variable is for some reason
if you are told that $p>0$ then you can, otherwise you cannot

anonymous · Answer

no it does not say whether it is positive or negtive

anonymous · Answer

then tell your math teacher you cannot solve this because when you get to this step 
$$-np>120$$ and you want to divide by $-p$ you don't know whether to change the inequality or not, so you cannot proceed

anonymous · Answer

okay. I will.

anonymous · Answer

you could still solve it, because you're multiplying the two variables together. if you multiply -5 and 2, you get -10. it's the same if you multiply 5 and -2, you get the same answer. it is entirely solvable