Answer:
turning point: (-3 , -16)
Step-by-step explanation:
y = x² + ax + b   pass(0,-7)(7,0)
(0)² + 0*a + b = -7   b= -7
(7)² + 7*a - 7 = 0    7a = 42   a = 6
 y = x² + ax + b = y = x² + 6x - 7 = (x+3)² - 16
(h,k): vertex      equation: y = a(x-h)² + k
h = -3 Â Â k=-16