For all x, (3x + 7)² = ?
A6x + 14
B6x² + 14
C9x² + 49
D9x² + 21x + 49
E9x² + 42x + 49
Can anyone explain how to make it step by step?
A6x + 14
B6x² + 14
C9x² + 49
D9x² + 21x + 49
E9x² + 42x + 49