Question

The line of symmetry for the quadratic equation y=ax^2-2x-3 is x=1. What is the value of "a"?

Answer 1

a = 1.

Explanation:

For the general vertex form:

y = a(x - b)^2 + c the line of symmetry is x = b.

y = ax^2 -2x - 3

y = a( x^2 - 2x/a) - 3

y = a[(x - 1/a)^2 - (1/a)^2] - 3

y = a(x - 1/a)^2 - 1/a - 3

Here the line of symmetry is x = 1 so we have:

1/a = 1

a = 1.