Problem: If the points (1,y1​) and (−1,y2​) lie on the graph of y=ax2+bx+c, and y1​−y2​=−6, then b equals:
Answer Choices:
A. −3
B. 0
C. 3
D. ac​
E. 2a+c​
Solution:
y1​=a+b+c and y2​=a−b+c∴y1​−y2​=2b. Since y1​−y2​=−6,2b=−6,b=−3.