# Graphs

The equation of the line of symmmetry of the curve y = x^2 + px + 21 is x = 4. Find the value of p.

Note by G Ooi
4 years, 7 months ago

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-9.25

- 4 years, 7 months ago

p = -8. Since, in the vertex form of the quadratic function, f(x) = a(x-h)^2 + k, x = h is the equation of the line of symmetry. In order to make x = 4 be the line of symmetry, f(x) must be (x-4)^2 + k. And this implies that the coefficient of x is -8. Hence, the answer.

- 4 years, 7 months ago