Add seven to both sides of the equal sign. Now you have 3x= -18
Then divide by three on each side. Now you have x= -6
Then plug it in.
-6^2-6(-6)+9
The answer to that is 9

a ) The domain:
x^4 - 16 x² ≥ 0
x² ( x² - 16 ) ≥ 0
x² - 16 ≥ 0
x² ≥ 16
x ∈ ( - ∞, - 4 ] ∪ [ 4 , + ∞ )b ) f ` ( x ) =

=
( 2 x³ - 16 x ) / √(x^4 - 16 x²)c ) The slope of the tangent line at x = 5:
f ` ( 5 ) = ( 2 * 125 - 16 * 5 ) / √ ( 625 - 400 ) = 170 / 15 = 34 / 3
The slope of the line normal to the graph at x = 5:
m = - 3 / 34
The answer would be -20 because you add and subtract your numbers to get 20