Monday, February 23, 2015

for the function y=2x^2+5X-k one of the zeros is at x=-4. Determine the other x intercept.Full thorough explanation of solution and steps

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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