(3x² -7x⁴) from (5x² - 3x⁸)
= 5x² - 3x⁸ - (3x² -7x<span>⁴ )
= </span> 5x² - 3x⁸ - 3x² + 7x<span>⁴
= </span>- 3x⁸ + 7x⁴ + 5x² <span>- </span><span>3x²
</span>
= - 3x<span>⁸ </span>+ 7x⁴ + 2x<span>²</span>
Answer: x=18
im assuming that this is a right angle
so if it is then that means the total of the angle should be 90 degrees. so 2x+3x should be equal to 90. Just combine like terms to get that 5x=90 and then isolate the variable (divide by 5 on both sides) so x ends up equaling 18.
so x=18
Average speed = total distance divided by total time.
In the first part, the car covered 490 km in 7 hours, but I think you mistyped the second part (“then covers a speed of 90km”) and a critical piece is missing to find the total distance and time.
A ) The domain:

x ≤ -4 and x≥ 4 or: x ∈ ( - ∞ , - 4 ) ∪ ( 4 , + ∞ )
b ) f ` ( x ) =

c ) The slope of the line normal to the graph at x = 5
m = -1 / f `(x)
f ` ( x ) =
m = - 3/34
I don’t see any of the problems so I’m guessing you would have to rewrite it