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# mathematics - quadratic inequality watch

1. how to Use b^2 - 4ac with a =3k, b= 8k + 6 and c = 9k- 2
to get - 44k^2 +120k +36 > 0 as an answer....?
2. (Original post by riskanya)
how to Use b^2 - 4ac with a =3k, b= 8k + 6 and c = 9k- 2
to get - 44k^2 +120k +36 > 0 as an answer....?
so you use b^2 - 4ac > 0 assuming two real roots

(8k+6)^2 - 4 x 3k x (9k-2)
(8k+6)(8k+6) -12k(9k-2) > 0
64k^2 + 96k + 36 - 108k^2 + 24k > 0

64 - 108 = -44k^2
96 +24 = 120k
therefore -44k^2 +120k +36 > 0
3. thank you

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