What substitution should be used to rewrite 4x^4-21x^2+20=0 as a quadratic equation

Mathematics

2 answers:

Andreyy893 years ago

8 0

let y = x^2

4y^2 -21y + 20 = 0

solve for y

then substitute back in to get x

azamat3 years ago

7 0

Answer:

4y^2 - 21y + 20 = 0

Step-by-step explanation:

As (4x^4 - 21x^2 + 20=0) being a biquadratic equation, meaning it is a 4-degree equation without the terms of degree 1 and 3.

To solve this particular case you only need to replace the variables of degree 4 and 2 for a new variable of degree 2 and 1 and solve it as regular quadratic equation and then undo the change.

* Using a new variable we can rewrite the equation:

Let y be the new variable;

y= x^2, then y^2= x^4

Then we have;

4y^2- 21y+20=0

Solve for y and then find X which will be the roots for the biquadratic equation.

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est scores for a statistics class had a mean of 79 with a standard deviation of 4.5. Test scores for a calculus class had a mean

Arte-miy333 [17]

Answer:

The z-score for the statistics test grade is of 1.11.

The z-score for the calculus test grade is 7.3.

Due to the higher z-score, the student performed better on the calculus test relative to the other students in each class

Step-by-step explanation:

Z-score:

In a set with mean $\mu$ and standard deviation $\sigma$ , the z-score of a measure X is given by:

$Z = \frac{X - \mu}{\sigma}$

The Z-score measures how many standard deviations the measure is from the mean. After finding the Z-score, we look at the z-score table and find the p-value associated with this z-score. This p-value is the probability that the value of the measure is smaller than X, that is, the percentile of X. Subtracting 1 by the p-value, we get the probability that the value of the measure is greater than X.

In this question:

The grade with the higher z-score is better relative to the other students in each class.

Statistics:

Mean of 79 and standard deviation of 4.5, so $\mu = 79, \sigma = 4.5$