Knowing the quadratic formula is:

 

Solve the equation $\displaystyle {x}^{{2}}+{4}{x}-{21}={0}$ 

STEP 1:  Substitute in for the -b. 

-b =

 

STEP 2: Find the Discriminant by plugging for the b² - 4ac (DO NOT SQUARE ROOT IT YET).    

b² - 4ac = 

 

STEP 3: Find the square root of the Discriminant by plugging for the √(b² - 4ac) 

√(b² - 4ac) =

 

STEP 4: Calculate the denominator by solving 2a. 

2a =

STEP 5: Simplify the radical and calculate the resulting solutions. Enter your answers as a list of integers or reduced fractions (NO DECIMALS), separated with commas.

EXAMPLES OF TYPING IN YOUR SOLUTIONS:

INTEGER SOLUTIONS: -3, 5
FRACTIONAL SOLUTIONS: -5/2, -3/4

 

 $\displaystyle {x}=$ Having trouble?  Check out Mr. Zimmermann's Video [+].