Writing Quadratic Equation in the
Form of ax2 + bx + c = 0, and Finding
the Value of a, b, and c.
Example 1. x2 = 5 – 2x
ax2 + bx + c = 0
x2 = 5 – 2x
x2 + 2x – 5 = 0
a = 1, b = 2, c = -5
Example 2. -11x + 4 = 2x2 – x - 5
ax2 + bx + c = 0
-11x + 4 = 2x2 – x - 5
= 2x2 – x + 11x – 5 – 4 (simplify)
0 = 2x2 + 10x – 9
a = 2, b = 10, c = -9
remember: (An equation ax2 + bx + c = 0 is the same as 0 = ax2 + bx + c.)
Example 3. 3x2 = 36
ax2 + bx + c = 0
3x2 = 36
3x2 – 36 = 0
a = 3, b = 0, c = -36
Example 4. (x + 2)2 = -6 + 3x
ax2 + bx + c = 0
(x + 2)2 = -6 + 3x
x2 + 4x + 4 = -6 + 3x
x2 + 4x – 3x + 4 + 6 = 0
x2 + x + 10 = 0
a = 1, b = 1, c = 10
Example 5. 11 = 3x + x2
ax2 + bx + c = 0
11 = 3x + x2
0 = x2 + 3x – 11
a =1, b = 3, c = -11

Writing quadratic equation

  • 1.
    Writing Quadratic Equationin the Form of ax2 + bx + c = 0, and Finding the Value of a, b, and c.
  • 2.
    Example 1. x2= 5 – 2x ax2 + bx + c = 0 x2 = 5 – 2x x2 + 2x – 5 = 0 a = 1, b = 2, c = -5
  • 3.
    Example 2. -11x+ 4 = 2x2 – x - 5 ax2 + bx + c = 0 -11x + 4 = 2x2 – x - 5 = 2x2 – x + 11x – 5 – 4 (simplify) 0 = 2x2 + 10x – 9 a = 2, b = 10, c = -9 remember: (An equation ax2 + bx + c = 0 is the same as 0 = ax2 + bx + c.)
  • 4.
    Example 3. 3x2= 36 ax2 + bx + c = 0 3x2 = 36 3x2 – 36 = 0 a = 3, b = 0, c = -36
  • 5.
    Example 4. (x+ 2)2 = -6 + 3x ax2 + bx + c = 0 (x + 2)2 = -6 + 3x x2 + 4x + 4 = -6 + 3x x2 + 4x – 3x + 4 + 6 = 0 x2 + x + 10 = 0 a = 1, b = 1, c = 10
  • 6.
    Example 5. 11= 3x + x2 ax2 + bx + c = 0 11 = 3x + x2 0 = x2 + 3x – 11 a =1, b = 3, c = -11