## Help with solving equations: (x+3)(x-3)>0, x^2-2x-15</= 0,

Complex numbers, rational functions, logarithms, sequences and series, matrix operations, etc.
isaiah45798
Posts: 8
Joined: Sun Jul 17, 2011 12:00 am
Contact:

### Help with solving equations: (x+3)(x-3)>0, x^2-2x-15</= 0,

Can someone please help or guide me with these problems.
Thanks in advance.
less than or equal to = </=

(x+3)(x-3)>0

x^2-2x-15</= 0

sin2x=sinx, 0</=x</=2pi

logx+log(x-3)=1

maggiemagnet
Posts: 358
Joined: Mon Dec 08, 2008 12:32 am
Contact:

### Re: Help with solving equations

(x+3)(x-3)>0

x^2-2x-15</= 0
To learn how to solve polynomial inequalities, try here.

The first one is already factored, so it's halfway done. For the second one, the first step would be to factor the quadratic.
sin2x=sinx, 0</=x</=2pi
To learn how to solve trig equations, try here.

A good first step would be to move the sine to the left-hand side, apply the double-angle identity to the first sine, and then factor. Then sovle each factor.
logx+log(x-3)=1
To learn how to solve log equations, try here.

A good first step would be to use log rules to combine the terms on the left-hand side. Then covert to the exponential form, and solve the rational equation you get out.

If you get stuck, please write back showing how far you've gotten. Thanks!

isaiah45798
Posts: 8
Joined: Sun Jul 17, 2011 12:00 am
Contact:

### Re: Help with solving equations: (x+3)(x-3)>0, x^2-2x-15</=

Thank you it all helped. I am stuck however on the trig equation. I am not sure what to do after I get 2sin(x)cos(x)=sin(x).

maggiemagnet
Posts: 358
Joined: Mon Dec 08, 2008 12:32 am
Contact:

### Re: Help with solving equations: (x+3)(x-3)>0, x^2-2x-15</=

Thank you it all helped. I am stuck however on the trig equation. I am not sure what to do after I get 2sin(x)cos(x)=sin(x).
A good first step would be to move the sine to the left-hand side, apply the double-angle identity to the first sine, and then factor. Then solve each factor.

Return to “Advanced Algebra ("pre-calculus")”