Penelope determined the solutions of the quadratic function by completing the square.

f(x) = 4x2 + 8x + 1
–1 = 4x2 + 8x

–1 = 4(x2 + 2x)

–1 + 1 = 4(x2 + 2x + 1)

0 = 4(x + 2)2

0 = (x + 2)2

0 = x + 2

–2 = x

What error did Penelope make in her work?

Penelope should have subtracted 1 from both sides instead of adding 1.
Penelope should have subtracted 4 from both sides instead of adding 1.
Penelope should have added 4 to both sides instead of adding 1.
Penelope should have subtracted 8 from both sides instead of adding 1.