Question

find the range of value of x such that the if the quadratic function f(x)=8+7x-x²=0 is positive.
( Can I request for steps and explanation? Thank you）
The answer is x＜-1 , x > 8.​

Answer 1

Answer:

For the parabola in the xy-plane, find the following.

y=x^2 - 4x - 12

(a) The x-intercepts:

evaluating at y=0

=> 0=x^2 - 4x - 12

=> 0=x^2 -6x+2x -12

=> (x-6) (x+2)

x=6 and -2

Answer 2

$x = - 5 \\ x = 10 \: \: \: \:$