Find the largest integer k such that the equation 5x^2 - kx + 8 - 2x^2 + 25 =0 has no real solutions
Simplify to... 3x^2 - kx + 33 = 0
Then in Desmos, graph
3x^2 - kx + 33 = 0
and
k = 0
Click on k = 0 and set the Step to 1
Change the range from "-10 to 10" to "0 to 25"
let the slider play from 25 to 0 and find the first one that has no line shown on it
First, let's simplify and combine all like terms.
After doing that, we get
\(3x^2-kx+33=0\)
Now, in order for the equation to have no real solutions, the descriminant must be less than 0.
The descriminant is \(b^2-4ac\), so we have the equation
\(k^2 - 4(33)(3) < 0\)
Since we are trying to find the largest, we set the two to equal each other and get
\(k^2 - 396 = 0\\ k^2 = 396\\ k \approx 19.89974\)
Rounding down, the largest k can be as an integer is 19.
So our answer is 19.
Thanks! :)