Answers

The Brainliest Answer!
2014-05-21T12:05:51+08:00
You are already giving a clue in "discriminant". hahaha

y = mx + b. since it passes thourgh (2,4), 4 = 2m + b. b = 4-2m.

y = mx + -2m + 4

3x^2 + 8y^2 = 24.

3x^2 + 8(mx - 2m + 4)^2 = 24

3x^2 + 8( m^2x^2 +2(mx)(-2m+4) + (-2m + 4)^2 ) = 24

3x^2 + 8(m^2 x^2 - 4m^2 x + 8mx + 4m^2 - 16m + 16) = 24

3x^2 + 8m^2x^2 - 32m^2 x + 64mx + 32m^2 - 128m + 128 = 24

(8m^2 + 3)x^2 + (64m - 32m^2)x + 32m^2 - 128m + 104 = 0

D/4 = (32m - 16m^2)^2 - (8m^2 + 3)(32m^2 - 128m + 104) = 0

= 256(2m-m^2)^2 - 8(8m^2 + 3)(4m^2 - 16m + 13) = 0

you can do the job now. after solving for the values of m,
substitute it in y = mx + 4 - 2m. then you're done. :-)

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