Answer:
Explanation:
-x² + 8x + 20 = b
-x² + 8x + 20 - b = 0
a = -1 ; b = 8 ; c = 20 - b
There is no real roots.
So, b² - 4ac < 0
Plug in a, b and c values
8²- 4(-1)(20-b) < 0
When we multiply (-1) and (-4), we will get 4
64 + 4(20 - b) < 0
64 + 4*20 - 4b < 0
64 + 80 - 4b < 0
144 - 4b < 0
Subtract 144 from both sides
-4b < -144
Divide both side by -4 and when we are dividing by (-4), < will change to >
b > -144/-4
b > 36
So, when value of b is greater than 36, the equation will have no real roots.