Question

Hyung-eun is solving the quadratic equation x^2−4x−12=0
by grouping. Her work is shown below. At which step does Hyung-eun first make an error?

x2−4x−12=0


x(x−6)+2(x−6)=0


Step1: x2+(−6x)+2x−12=0

Step 2: (x2+(−6x))+(2x−12)=0

Step 3: x(x+(−6))+2(x−6)=0

Step 4: (x+6)(x−2)=0

Step 5: x+6=0
or x−2=0

x=−6
or x=2


(1 point)
Responses

Step 1
Step 1

Step 4
Step 4

Step 3
Step 3

Step 2

Answer 1

Step 4

Explanation: From x(x−6)+2(x−6)=0 you should factor (x−6) to get (x+2)(x−6)=0. Writing (x+6)(x−2)=0 in Step 4 is incorrect.