Question

Karim is solving the quadratic equation x2+5x−24=0
by grouping. His work is shown below. Determine the first step at which Karim makes an error.

Step 1: x2+8x+(−3x)−24=0

Step 2: (x2+8x)+(−3x−24)=0

Step 3: x(x+8)+3(x+8)=0

Step 4: (x+8)(x+3)=0

Step 5: x+8=0
or x+3=0

x=−8
or x=−3


(1 point)
Karim's first mistake occurs at Step
.

Answer 1

Step 3.

In Step 2 the second group is −3x − 24, which factors as −3(x + 8), not +3(x + 8).