Squaring a Binomial {ACT}

For all x, (3x + 1)² = ?
A.)  6x + 2
B.)  9x² + 1
C.)  9x² + 3x + 1
D.)  3x² + 1
E.)  9x² + 6x + 1

(3x + 1)²
= (3x + 1)(3x + 1)   {when squaring a binomial, multiply it by itself}
= 3x(3x) + 3x(1) + 1(3x) + 1(1)   {used foil method}
= 9x² + 3x + 3x+ 1   {multiplied through}
= 9x² + 6x + 1   {combined like terms}

E.)

- Algebra House