A community for students.
Here's the question you clicked on:
 0 viewing
anonymous
 one year ago
Last problem! Help for medal.
I need help with just one more inequality equation...
x^2  x  15 > 15
anonymous
 one year ago
Last problem! Help for medal. I need help with just one more inequality equation... x^2  x  15 > 15

This Question is Closed

anonymous
 one year ago
Best ResponseYou've already chosen the best response.0Would you like me to explain?

UsukiDoll
 one year ago
Best ResponseYou've already chosen the best response.0@_greatmath7 thanks for providing an explanation in addition to the direct answer. :)

anonymous
 one year ago
Best ResponseYou've already chosen the best response.0Let's solve your inequality stepbystep. x^2x15>15 Let's find the critical points of the inequality. (Subtract 15 from both sides): x^2x1515=1515 You then receive: x^2x30=0 (Factor left side of equation):(x+5)(x6)=0 (Set factors equal to 0):x+5=0 and x=0

anonymous
 one year ago
Best ResponseYou've already chosen the best response.0Oh I see. Thank you very much! :)

UsukiDoll
 one year ago
Best ResponseYou've already chosen the best response.0o_0 \[\LARGE x^2  x  15 > 15\] first we subtract 15 from both sides \[\LARGE x^2  x  1515 > 1515\] \[\LARGE x^2  x  30 > 0\] then we have to factor. our last term is 30 and the middle term is 1 6 x 5 is the only combination that can work for this quadratic equation because 6 x 5=30 65 = 1 Therefore \[\LARGE (x6)(x+5) > 0\] now we solve \[\LARGE (x6)(x+5) > 0\] by splitting this up into two cases \[\LARGE (x6) > 0\] \[\LARGE (x+5) > 0\] solving for an inequality is the same as solving for an equation \[\LARGE x6 > 0\] \[\LARGE x6+6 > 0+6\] \[\LARGE x > 6\] \[\LARGE x+5 > 0\] \[\LARGE x+55 > 05\] \[\LARGE x > 5\] time to switch the inequality sign \[\LARGE x < 5\]

UsukiDoll
 one year ago
Best ResponseYou've already chosen the best response.0on the number line since we have < we have an open circle dw:1439510309024:dw

UsukiDoll
 one year ago
Best ResponseYou've already chosen the best response.0for example x < 5 the mouth of < is going on the right, but actually we have to shade the left side on the number line according to the tail similarly x > 6 the > is going left, but actually we have to shade to the right on the number line according to the tail.

anonymous
 one year ago
Best ResponseYou've already chosen the best response.0I'm sorry, but I've gotten a bit lost on the sign switching step. Could you explain that again?

UsukiDoll
 one year ago
Best ResponseYou've already chosen the best response.0I got a bit confused on that one too... I think it has something to do with the negative number. I know that if you divide both sides by a negative number the inequality signs switch, so I'm assuming that since we have a negative number as one of the solutions, the inequality signs switch. But what I've read is that only swapping sides, and multiplication/division by negative numbers switch the inequality signs so x > 5 swapping sides 5 < x but it's a standard to have that variable x on the left hand side.

UsukiDoll
 one year ago
Best ResponseYou've already chosen the best response.0ah..maybe switching x> 5 by swapping sides might be it? 5 < x but nobody writes it like that even though it's still the correct answer.

anonymous
 one year ago
Best ResponseYou've already chosen the best response.0Oops duh. Thank you for your help as well. :)

anonymous
 one year ago
Best ResponseYou've already chosen the best response.0So it would be 6 < x > 5

UsukiDoll
 one year ago
Best ResponseYou've already chosen the best response.0x.x I would just leave it as x< 5 and x >6

anonymous
 one year ago
Best ResponseYou've already chosen the best response.0What confuses me is how x > 5 turns into x< 5

UsukiDoll
 one year ago
Best ResponseYou've already chosen the best response.0it probably because x > 5 doesn't make sense. x can't be greater than 5 the number lines either look like dw:1439512229503:dw or dw:1439512254356:dw

UsukiDoll
 one year ago
Best ResponseYou've already chosen the best response.0^ that's just an example by the way the first number line's notation is 2 < x < 3 in order from smallest to greatest the second number line's notation is x < 2 or x >3

anonymous
 one year ago
Best ResponseYou've already chosen the best response.0If x is greater than 6, wouldn't it also be greater than 5? (I'm sorry if I'm becoming cumbersome. I am just having a hard time understanding)

UsukiDoll
 one year ago
Best ResponseYou've already chosen the best response.0no. x > 6 x < 5 http://www.wolframalpha.com/input/?i=solve+x%5E2++x++15+ >+15 I already mentioned that when putting the inequality on the number line it should either be in the format of 2<x<3 dw:1439514392007:dw or x < 2 or x>3 dw:1439514398312:dw

UsukiDoll
 one year ago
Best ResponseYou've already chosen the best response.0you know what's off? only multiplying or dividing with negative numbers switches the signs.. a part of me wants x> 5 to be that answer. but stupid wolfram has it at x <5 if I switch the sides on x >5 and change the inequality sign 5<x which is correct, but the standard is x on the left hand side even though 5 < x is correct.

UsukiDoll
 one year ago
Best ResponseYou've already chosen the best response.0another example Example: 12 < x + 5 If we subtract 5 from both sides, we get: 12  5 < x + 5  5 7 < x That is a solution! But it is normal to put "x" on the left hand side ... ... so let us flip sides (and the inequality sign!): x > 7 Do you see how the inequality sign still "points at" the smaller value (7) ? And that is our solution: x > 7 source: http://www.mathsisfun.com/algebra/inequalitysolving.html
Ask your own question
Sign UpFind more explanations on OpenStudy
Your question is ready. Sign up for free to start getting answers.
spraguer
(Moderator)
5
→ View Detailed Profile
is replying to Can someone tell me what button the professor is hitting...
23
 Teamwork 19 Teammate
 Problem Solving 19 Hero
 Engagement 19 Mad Hatter
 You have blocked this person.
 ✔ You're a fan Checking fan status...
Thanks for being so helpful in mathematics. If you are getting quality help, make sure you spread the word about OpenStudy.