How do you solve for x?
and in
(x+3)(x-3)>0
and in
abs(x-3)<7
Favorite Answer
1)logx+log(x-3)=1
*Remember since no base is given you are therefore using base 10
For this we use the formula log m + log n = log (m*n)
Here we have m = x and n = (x – 3)
logx+log(x-3)=1 Write original equation
log [ x * ( x – 3)] = 1
10 log [ x * ( x – 3)] = 10 1 Exponentiate each side using base 10
[ x * ( x – 3)] = 10
x2 – 3x = 10
x2 – 3x – 10 = 0Rewrite in simple form
(x – 5) (x + 2) = 0Factor
*Remember the zero product property: when ab = 0, the a = 0, b= 0, or both = 0
(x-5) = 0(x + 2) = 0 Solve both
x = 5x = -2
Check both answers:
When x = 5
log5+log(5-3)=1
log5+log(2)=1
1 = 1
When x = 2
log2+log(2-3)=1
log2+log(-1)=1
log (-1) is not defined, so not a real solution
2)(x+3)(x-3)>0
Use the zero product property as above, just use > instead of =
(x + 3) > 0, subtract 3 from both sides
x < -3 (x-3) > 0, add 3 to both sides
x > 3
You could also graph this one to see which direction to “shade” if you need to graph it as well.
3)|x – 3| < 7 The trick here is to remember that you need both the positive AND the negative values. The positive value: |x – 3| < 7 x – 3 < 7, add three to both sides x < 10 The negative value: (because you set it “equal” to a negative number) *Don’t forget that when you set this to the negative value you need to reverse the inequality sign* x – 3 > -7, add 3 to both sides
x > -4
Your final answer is: -4 < x < 10 Hope this helped!! If you are still confused I would suggest getting some extra problem sets from your teacher so you don’t fall too far behind before the school year starts off. Good luck!
x>3 or x<-3
-4
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