Question

[rachael724]

Solve | 2x + 5 | < 13

a. -8 < x < 5
b. -5 < x < 8
c. 5 < x < 8
d. -8 < x < -5
e. none of these


Would d be the correct answer?

 

[tkhunny]

I'm going with e.

d. would be correct IF is said -9 < x < 4

How were you working it and what answer were you getting?

 

[Unco]

You can rewrite it as

-13 < 2x + 5 < 13

Can you go from there?

 

[ting]

Did you substutute in possible values of x, from d and found that the satisfy the equality?

Solve | 2x + 5 | < 13

You could check the solution by setting up and solving the following two inequalities:

2x + 5 < 13

Solve for x

and

2x + 5 > -13

Solve for x

~~~~~~~~~~~~~~~~~~~~~~~~~

Or square both sides to ensure the LHS is positive and solve the resulting quadratic inequality.

(2x+5)^2 < 13^2

4x^2 + 20x - 144 < 0

x^2 + 5x -36 < 0

Solve for x.

 

[soroban]

Hello, rachael724!

There's a typo in the problem, isn't there?

Solve | 2x + 3 | < 13

(a) -8 < x < 5
(b) -5 < x < 8
(c) 5 < x < 8
(d) -8 < x < -5
(e) none of these

Would d be the correct answer? . . . . no

We solve it like this: . -13 . < . 2x + 3 . < . 13

Subtract 3: . . . . . . . . . .-16 . < . 2x . < . 10

Divde by 2: . . . . . . . . . . . -8 . < . x . < . 5

. . . Answer: .(a)