Which of these choices are quadratic equations? Check all that apply. A. 2x – 1 = 0
B. 2x2 - 1 = 0
C. 2x2 - 1
D. 3x2 + 5x - 1 = 0
E. x - x² +5=0
F. - 4x2 + x = 0

Quadratic Equations ⇒ D, E, F

Step-by-step explanation:

Let us say that each of these equations can only be defined as a quadratic equation if it can be factored / solved through completing the square / application of quadratic formula as solve for the value of x;

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step-by-step explanation:

take the logarithm of both sides (the base of the log doesn't matter):

apply the exponent property - this says that :

distribute the log terms on both sides:

group like terms together:

divide through both sides by the coefficient on :

you can do some additional rewriting here using the properties of the logarithm to simplify things if you like: