# Find the equation of a quadratic function in standard form given that its graph contains the points. (−3, 8), (2, −12), and (1, 0)?

Update:

pls can someone else answer

### 3 Answers

Relevance

- QuevvyLv 44 years ago
y = ax^2+bx+c and plug in the points you have

Start with (1,0).

0 = a+b+c

then (-3, 8)

8 = 9a - 3b + c

then (2,-12)

-12 = 4a + 2b + c

Use a matrix

[1 1 1]

[9 -3 1] * [abc] = b

[4 2 1]

where b =

[0]

[8]

[-12]

to get

[abc] = A^-1*b

to get a = -2, b = -6, c = 8

Then we have y = -2x^2 - 6x + 8. = -2(x^2 + 3x - 4) = -2(x+4)(x-1)

Plug in the points to double-check your work.

[Note the negative sign that alex is missing.]

- JeffLv 74 years ago
Hint: Let y = f(x) = Ax² + Bx + C

Use the 3 given points to set up 3 equations in A, B, C and solve.

Still have questions? Get your answers by asking now.