5.6 Quadratic Formula & Discriminant
Quadratic Formula (Yes, it’s the one with the song!) If you take a quadratic equation in standard form (ax 2 +bx+c=0), and you complete the square, you will get the  quadratic formula !
When to use the Quadratic Formula Use the quadratic formula when you can’t factor to solve a quadratic equation.  (or when you’re stuck on how to factor the equation.)
Discriminant:  b 2 -4ac The discriminant tells you how many solutions and what type you will have. If the discrim: Is positive : 2 real solutions   Is negative : 2  imaginary    solutions   Is zero : 1 real solution
Examples Find the discriminant and give the number and type of solutions. 9x 2 +6x+1=0 a=9, b=6, c=1 b 2 -4ac=(6) 2 -4(9)(1)   =36-36=0 1 real solution 9x 2 +6x-4=0 a=9, b=6, c=-4 b 2 -4ac=(6) 2 -4(9)(-4) =36+144=180 2 real solutions c.   9x 2 +6x+5=0 a=9, b=6, c=5 b 2 -4ac=(6) 2 -4(9)(5) =36-180=-144 2 imaginary solutions
Examples 3x 2 +8x=35 3x 2 +8x-35=0 a=3, b=8, c= -35 OR
-2x 2 =-2x+3 -2x 2 +2x-3=0 a=-2, b=2, c= -3

6.5 quadratic formula & the discriminant

  • 1.
    5.6 Quadratic Formula& Discriminant
  • 2.
    Quadratic Formula (Yes,it’s the one with the song!) If you take a quadratic equation in standard form (ax 2 +bx+c=0), and you complete the square, you will get the quadratic formula !
  • 3.
    When to usethe Quadratic Formula Use the quadratic formula when you can’t factor to solve a quadratic equation. (or when you’re stuck on how to factor the equation.)
  • 4.
    Discriminant: b2 -4ac The discriminant tells you how many solutions and what type you will have. If the discrim: Is positive : 2 real solutions Is negative : 2 imaginary solutions Is zero : 1 real solution
  • 5.
    Examples Find thediscriminant and give the number and type of solutions. 9x 2 +6x+1=0 a=9, b=6, c=1 b 2 -4ac=(6) 2 -4(9)(1) =36-36=0 1 real solution 9x 2 +6x-4=0 a=9, b=6, c=-4 b 2 -4ac=(6) 2 -4(9)(-4) =36+144=180 2 real solutions c. 9x 2 +6x+5=0 a=9, b=6, c=5 b 2 -4ac=(6) 2 -4(9)(5) =36-180=-144 2 imaginary solutions
  • 6.
    Examples 3x 2+8x=35 3x 2 +8x-35=0 a=3, b=8, c= -35 OR
  • 7.
    -2x 2 =-2x+3-2x 2 +2x-3=0 a=-2, b=2, c= -3