Question

If (x + 1)(x - 3) = 5, then which of the following statements is true?

x + 1 = 0 or x - 3 = 0

x + 1 = 5 or x - 3 = 5

x - 4 = 0 or x + 2 = 0

Answer 1

Simplify both sides of the equation.
\[x^2−2x−3=5\]
and subtract 5 from both sides
\[x^2−2x−3−5=5−5\]
\[x^2−2x−8=0\]
Factor left side of equation.
\[(x+2)(x−4)=0 \]
Set factors equal to 0
\[x+2=0 or x−4=0 \]
which would bring us to\( x=−2\) or \(\ x=4 \)

Answer 2

This isn't FIOL right?

Answer 3

So basically the answer should be \(x - 4 = 0\)or \(x + 2 = 0 \)

Answer 4

There was FOIL used in the first step.

Answer 5

All 3 choices are incorrect.
Are you sure you copied the second choices correctly?

Answer 6

@calculusxy
That is not correct.

Answer 7

How are all three incorrect?

Answer 8

Sorry, you are correct. One choice is correct.
It's the one that gives the correct solutions that @AloneS found.

Answer 9

Wait so i'm wrong?

Answer 10

One of the three choices of the original problem that was posted is correct.

Answer 11

@AloneS is correct.
One of the choices is @AloneS 's solution.

Answer 12

What is incorrect is a statement that @calculusxy made above.

Answer 13

How can you confirm that the option works?

Answer 14

If (x + 1)(x - 2) = 0, then one of the factors must equal zero.
That is how we solve the equation.

If (x + 1)(x - 3) = 5, we cannot set the factors equal to 5 and solve.
That simply does not work.

Answer 15

I see

Answer 16

Look at the solution we have:
x = 4 or x = -2
One of the choices is the same as that solution.