# check math

posted by
**Anonymous**
.

Here are my answers. Can you check if I got the right answers? Thank you!

(x+3)(x-3)>0 answer: x<-3 or x>3

x^2-2x-15</=0 answer: -3</=x</=5

12x^2=3x answer: x=1/4

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

lx-3l<7 answer: (-oo,oo)

(x+1)^2(x-2)+(x+1)(x-2)^2=0

answer: x=-1,2,1/2

27^(2x)=9^(x-3)answer: x=-3/2

logx+log(x-3)=1 answer: x=-2, 5

(x+3)(x-3)>0 answer: x<-3 or x>3 **ok**

x^2-2x-15</=0 answer: -3</=x</=5 **ok**

12x^2=3x answer: x=1/4 **also x = 0**, (12x^2 - 3x = 0 ---> x(12x-3)=0 )

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

no. recall that sin2x = 2(sinx)(cosx)

so

2(sinx)(cosx)-sinx=0

sinx(2cosx -1=0

sinx=0 or cosx=1/2

then x=0,pi,2pi from the first

or x = pi/3 (60º) or 5pi/3 (300º)

lx-3l<7 answer: (-oo,oo) **No, -4≤x≤10 **

(x+1)^2(x-2)+(x+1)(x-2)^2=0

answer: x=-1,2,1/2 **ok**

27^(2x)=9^(x-3)answer: x=-3/2 **ok**

logx+log(x-3)=1 answer: x=-2,5
**Your answer of x=-2 does not work in logx, you cannot take the log of a negative number. So just x=5 **