Use the discriminant to determine all values of k which would result in the graph of the equation y = -2x2 + kx – 18 being tangent to the x-axis.

k = ±12

Step-by-step explanation:

Equation of the graph is,

y = -2x² + kx - 18

Discriminant of a quadratic equation, y = ax² + bx + c is defined by

Discriminant = √(b²- 4ac)

If √(b²- 4ac) = 0,

Equation will have one real solution.

Discriminant of the the given equation = √[k² - 4(-2)(-18)]

Since, graph of the equation is tangent to the x-axis, there will be one real solution.

Therefore, √[k² - 4(-2)(-18)] = 0

k² - 144 = 0

k = ±√144

k = ±12

37

step-by-step explanation: