Question

F(x) = 2x2 – 4x – 3

0 = 2x2 – 4x – 3

3 = 2(x2 – 2x)

3 + 1 = 2(x2 – 2x + 1)

4 = 2(x – 1)2

2 = (x – 1)2

± = x – 1

1 ± = x

Mica is solving for the zeros of a quadratic function by completing the square. Her work is shown. What error did Mica make?




ANSWER CHOICES
Mica should have set each x = 0 instead of f(x).
Mica should have added 2 to 3 instead of 1.
Mica should have multiplied both sides by 2 instead of dividing.
Mica should have subtracted 1 from both sides instead of adding.

Answer 1

Mica should have added 2 to 3 instead of 1.

Answer 2

Mica should have added 2 to 3 instead of 1 to 3.

She factored out a 2 on the righthand side, so adding 1 within the parentheses is equivalent to adding 2 outside the parentheses. Since this is an equation, what we do to one side, we must do to the other, so Mica should've added 2 to the lefthand side.