We have y= 2x^2 + 5x - k which is a quadratic equation and
we are given that one of the roots is at x = -4.
The roots
of 2x^2 + 5x - k lie at :
x = -5/4 + sqrt (25 + 8k)/4 and x
= -5/4 - sqrt (25 + 8k)/4
As one of the roots is
-4
-5/4 - sqrt (25 + 8k)/4 =
-4
=> -5 - sqrt(25 + 8k) =
-16
=> sqrt(25 + 8k) =
11
=> (25 + 8k) =
121
=> (25 + 8k) =
121
=> 8k =
96
=> k = 12
The other
root is at x = -5/4 + sqrt (25 + 8k)/4
=> x = -5/4 +
sqrt (25 + 96)/4
=> -5/4 +
11/4
=> 6/4
=>
3/2
As x = 3/2 is the other root, this is also the point
where the other x-intercept lies.
The other
x-intercept of y = 2x^2 + 5x - k is (3/2, 0).
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