use the discriminant example 1 number of solutions equation ax 2 + bx + c = 0 discriminant b 2 –...
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![Page 1: Use the discriminant EXAMPLE 1 Number of solutions Equation ax 2 + bx + c = 0 Discriminant b 2 – 4ac a. x 2 + 1= 0 b. x 2 – 7 = 0 c. 4x 2 – 12x + 9 = 0](https://reader036.vdocuments.us/reader036/viewer/2022082319/5697c01e1a28abf838cd0fb2/html5/thumbnails/1.jpg)
Use the discriminant
EXAMPLE 1
Number of solutions
Equationax2 + bx + c = 0
Discriminantb2 – 4ac
a. x2 + 1= 0
b. x2 – 7 = 0
c. 4x2 – 12x + 9 = 0
02 – 4(1)(1) = –4 No solution
02 – 4(1)(– 7) = 28 Two solutions
(–12)2 –4(4)(9) = 0 One solution
The Number i The equation x2 + 1= 0 has no real solutions. In a future course, you will learn that the imaginary number i, defined as , and its opposite are solutions.
![Page 2: Use the discriminant EXAMPLE 1 Number of solutions Equation ax 2 + bx + c = 0 Discriminant b 2 – 4ac a. x 2 + 1= 0 b. x 2 – 7 = 0 c. 4x 2 – 12x + 9 = 0](https://reader036.vdocuments.us/reader036/viewer/2022082319/5697c01e1a28abf838cd0fb2/html5/thumbnails/2.jpg)
Find the number of solutions
EXAMPLE 2
Tell whether the equation 3x2 – 7 = 2x has two solutions, one solution, or no solution.
SOLUTION
STEP 1 Write the equation in standard form.
3x2 – 7 = 2x
3x2 – 2x – 7 = 0
Write equation.
Subtract 2x from each side.
![Page 3: Use the discriminant EXAMPLE 1 Number of solutions Equation ax 2 + bx + c = 0 Discriminant b 2 – 4ac a. x 2 + 1= 0 b. x 2 – 7 = 0 c. 4x 2 – 12x + 9 = 0](https://reader036.vdocuments.us/reader036/viewer/2022082319/5697c01e1a28abf838cd0fb2/html5/thumbnails/3.jpg)
Find the number of solutionsEXAMPLE 2
STEP 2 Find the value of the discriminant.
b2 – 4ac = (–2)2 – 4(3)(–7)
= 88
Substitute 3 for a, – 2 for b,
and –7 for c.
Simplify.
The discriminant is positive, so the equation has two solutions.
ANSWER
![Page 4: Use the discriminant EXAMPLE 1 Number of solutions Equation ax 2 + bx + c = 0 Discriminant b 2 – 4ac a. x 2 + 1= 0 b. x 2 – 7 = 0 c. 4x 2 – 12x + 9 = 0](https://reader036.vdocuments.us/reader036/viewer/2022082319/5697c01e1a28abf838cd0fb2/html5/thumbnails/4.jpg)
Tell whether the equation has two solutions, one
solution, or no solution.1. x2 + 4x + 3 = 0
GUIDED PRACTICE for Examples 1 and 2
ANSWER two solutions
2. 2x2 – 5x + 6 = 0 ANSWER no solution
3. – x2 + 2x = 1 ANSWER one solution