How do you solve the system 9x^2+4y^2=36 and -x+y=-4?

1 Answer
Sep 30, 2016

Substitute x - 4 for y in 9x^2 + 4y^2 = 36 to discover that there are no real roots for the resulting quadratic, therefore, the line does not intersect with the ellipse.

Explanation:

Given:
y = x - 4
9x^2 + 4y^2 = 36

9x^2 + 4(x - 4)^2 = 36

9x^2 + 4(x^2 - 8x + 16) = 36

13x^2 - 32x + 64 = 36

13x^2 - 32x + 28 = 0

b^2 - 4(a)(c) = (-32)^2 - 4(13)(28) = -432

There are no real roots, therefore, the line does not intersect with the ellipse