Mathematics 29 Online
OpenStudy (anonymous):

3-x<1 is this correct? (-infty, -4]

OpenStudy (anonymous):

it tells me its incorrect, am i typing it wrong?

OpenStudy (anonymous):

-x < -2 x > 2

OpenStudy (anonymous):

(2, inf)

OpenStudy (anonymous):

-3-x<1 sorry i typed the problem wrong

OpenStudy (anonymous):

(-4,inf)

OpenStudy (anonymous):

thats right but can you tell me why?

OpenStudy (anonymous):

-3-x<1 3+x>-1 x>-4

OpenStudy (anonymous):

$-3-x<1$ $-3<x+1$ $-4<x$ x is GREATER than -4

OpenStudy (anonymous):

well i got that but why isnt it -$\infty$

OpenStudy (anonymous):

-x < 4 x > -4 when dividing both sides by a negative the inequality sign flips

OpenStudy (anonymous):

oh yeah i knew that... lol

OpenStudy (anonymous):

oh ok so you also understand why its (-4,inf) right

OpenStudy (anonymous):

you can multiply by a negative number and change signs if you like. but you can also just add to both sides to assure that the coefficient of x is positive

OpenStudy (anonymous):

$-x>10$ $-x+x>10+x$ $0>10+x$ $-10>x$

OpenStudy (anonymous):

yeah that might be easier so i dont forget, thanks