Question

Write an equation (any form) for the quadratic graphed below. Y=

Answer 1

y = -2x^2 - 4x - 1

Explanation:

We can see that the graph passes through (-2, -1), (-1, 1) and (0, -1).

Let's solve

ax^2 + bx + c = y

a(-2)^2 + b(-2) + c = -1

4a - 2b + c = -1

a(-1)^2 + b(-1) + c = 1

a - b + c = 1

a0^2 + b0 + c = -1

c = -1

we got c = -1 so we input it into the other 2

4a - 2b - 1 = -1

4a - 2b = 0

2a - b = 0

2a = b

a - b - 1 = 1

a - b = 2

a = b + 2

Let's input b = 2a

a = 2a + 2

-a = 2

a = -2

b = 2a = 2*(-2) = -4

c = -1

y = -2x^2 - 4x - 1