A quadratic function is given by f:x------ax2+b

If the two points A(2, 2) and B (0, -8) are on the graph of the function, then find a and b.

mother of student needing help!!!

Hi,

The relationship between the x and y coordinates of points on the graph is given by

y = a x2 + b. You have two points on the graph, (2,2) and (0,-8) and hence these points must satisfy the relationship above. That is 2 = a 22 + b

-8 = a 02 + b

Thus 2 = 4 a + b

-8 = b

From the second equations above, b = -8 and if you substitute this value into the first equation you can find a.

Cheers,
Penny
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