Answer:
k = 2
Step-by-step explanation:
Given
5x² - kx + 40
Solution: ⅘
Required
Find k
If the solution is ⅘, then
5x² - kx + 40 = 0 where x = ⅘
Substitute ⅘ for x
5(⅘)² - k(⅘) + 40 = 0
5(16/25) - k(4/5) + 40 = 0
Multiply through by 25
5(16) - 5 * k(4) + 40 = 0
80 - 20k + 40 = 0
Collect like terms
-20k = 0 - 80 + 40
-20k = -40
Divide both sides by-20
k = 2
