Mathieu is finding the x-intercepts of the function f (x) = x2 + 4x + 3. His work is shown below

. Which error did Mathieu make?

I can't see Mathieu's work but I will show the right steps and maybe you can find where Mathieu went wrong.

f (x) = x^2+4x+3

f (x) = (x+3) (x+1) Since 3*1=3 and 3+1=4

The x-intercepts can be found by setting y to 0 and solving for x

(in other words replace that f (x) thing with 0 and solve for x)

0 = (x+3) (x+1)

Now set both factors equal to 0

x+3=0 or x+1=0

x = -3 x=-1

The x-intercepts are at (-3,0) and (-1,0)