Question

2x2 – 9x + 2 = –1

The discriminant is less than 0, so there are two real roots.
The discriminant is less than 0, so there are two complex roots.
The discriminant is greater than 0, so there are two real roots.
The discriminant is greater than 0, so there are two complex roots.

Answer 1

C) The discriminant is greater than 0, so there are two real roots

Explanation:

Discriminant

`b^2-4ac\quad\textsf{when}\:ax^2+bx+c=0`

`\textsf{when }\:b^2-4ac > 0 \implies \textsf{two real roots}`

`\textsf{when }\:b^2-4ac=0 \implies \textsf{one real root}`

`\textsf{when }\:b^2-4ac < 0 \implies \textsf{no real roots}`

`2x^2-9x+2=-1`

`\implies 2x^2-9x+3=0`

`\implies a=2, b=-9, c=3`

`\begin{aligned}b^2-4ac &=(-9)^2-4(2)(3)\\& =81-24\\&=57 > 0\implies \textsf{two real roots}\end{aligned}`