Answer:
x = 3/2 ± √(61/20)
Step-by-step explanation:
5x² - 15x - 4 = 0
Add 4 to both sides.
5x² - 15x = 4
The coefficient of 5x² is 5, divide both sides by 5.
x² - 3x = 4/5
The coefficient of -3x is -3. Let b=-3.
Then we need to add (b/2)^2=9/4 to both sides to complete the square.
Add 9/4 to both sides.
x² - 3x + 9/4 = 61/20
Factor left side.
(x-3/2)² = 61/20
Take square root of both sides.
x-3/2 = ± √(61/20)
Add 3/2 to both sides.
x = 3/2 ± √(61/20)
