Question

Determines the length of the chord intercepted by the straight line of equation y = -4x + 8 on the parabola of equation y = -3x^2 + 5x + 2.

Answer 1

Let's work out the intercepted points:

-4x + 8 = -3x^2 + 5x + 2

<=>

3x^2 - 9x + 6 = 0

<=>

x^2 - 3x + 2 = 0

<=>

(x - 1)(x - 2) = 0

<=>

x = 1 => y = -4 x 1 + 8 = 4 => A(1, 4)

and

x = 2=> y = -4 x 2 + 8 = 0 =>B(2, 0)

Then, length of chord AB is calculated by:

L = sqrt [(2 - 1)^2 + (0 - 4)^2)] = ~4.123