16/11/2021
QUADRATIC EQUATION
STEPS USING THE QUADRATIC FORMULA

x2−4x−5=0
All equations of the form ax2+bx+c=0 can be solved using the quadratic formula: 2a−b±b2−4ac. The quadratic formula gives two solutions, one when ± is addition and one when it is subtraction.
x2−4x−5=0
This equation is in standard form: ax2+bx+c=0. Substitute 1 for a, −4 for b, and −5 for c in the quadratic formula, 2a−b±b2−4ac.
x=2−(−4)±(−4)2−4(−5)
Square −4.
x=2−(−4)±16−4(−5)
Multiply −4 times −5.
x=2−(−4)±16+20
Add 16 to 20.
x=2−(−4)±36
Take the square root of 36.
x=2−(−4)±6
The opposite of −4 is 4.
x=24±6
Now solve the equation x=24±6 when ± is plus. Add 4 to 6.
x=210
Divide 10 by 2.
x=5
Now solve the equation x=24±6 when ± is minus. Subtract 6 from 4.
x=2−2
Divide −2 by 2.
x=−1
The equation is now solved.
x=5x=−1