Respuesta :
y = 3x² + 18x
factor out the leading coefficient
y = 3(x²+6x)
Complete the square
 coefficient of the x term: 6
 divide it in half: 3
 square it: 3²
 use 3² to complete the square:
y = 3(x²+6x + 3²) - 3·3²
 = 3(x+3)² - 3·3²
 = 3(x+3)² - 27
vertex (-3, -27)
factor out the leading coefficient
y = 3(x²+6x)
Complete the square
 coefficient of the x term: 6
 divide it in half: 3
 square it: 3²
 use 3² to complete the square:
y = 3(x²+6x + 3²) - 3·3²
 = 3(x+3)² - 3·3²
 = 3(x+3)² - 27
vertex (-3, -27)