Answer:
Step-by-step explanation:
y = - 3x² - 24x - 42
y = - 3( x² + 8x + 14 )
y = - 3( x² + 2·4·x + 16 - 16 + 14 )
y = - 3[ ( x + 4 )² - 2 ]
y = - 3( x + 4 )² + 6
