Study Guide Quadratic Formula

What does the discriminant tell us?

• The maximum or minimum

• The y-intercept

• The number and type of solutions

• The axis of symmetry

What should you do first in solving this equation?
x² + 6x - 13 = 3

• Get factored form

• Write down: a=1, b=6, c=-13

• Make it equal 0 by subtracting 3 on each side

• Type it all in a calculator.

When the discriminant is (a)   there will be two imaginary roots.

• Negative

• Zero

• Positive

Find the sum of the solutions.

5x² + 6x - 1 = 0 (use 2 decimal places)

• Use quadratic formula.

• Add the values of x.

• True. Both x=2 and x=-3 are roots.

• False. x=2 is a root, but not x=-3.

• False. x=-3 is a root, but not x=2.

• False. Neither x=2 or x=-3 are roots.

Use the quadratic formula to find the solutions for

y = -x² - 5x + 12

• No Real Solution

• 
• 
• 

Solve using the Quadratic Formula

6x² + 12x - 1 = 0

• x = 0.08, -2.08

• x = -0.08, 2.08

• x = -0.08, -1.91

• x = 0.08, 1.19

Is Allys' work correct or incorrect. If incorrect identify and explain the error.

• Correct

• Incorrect: The -5 at the beginning of plugging into the quadratic formula should be +5

• Incorrect: The 24 should have been added to put the problem into standard form.

• Incorrect: The -5 should not have been plugged into the parentheses.

Find the error - This problem was solved using the quadratic formula.

• It's a trick question. There is not an error.

• 81 - 40 should have been 81 + 40

• The zero can't be on the left side when the problem is in standard form.

• The "b" term is incorrectly plugged into the formula before solving.

Is the quadratic formula used correctly or incorrectly in this problem? If incorrect, identify the error.

• Incorrect: the equation can't be set equal to "y"

• Incorrect: the b-term is plugged in incorrectly

• Correct

• Incorrect: the 4+12 should be 4-12 under the radical.