It is definitely not a primary source: this would be a book itself.

Now, is it a tertiary source? I don't think so: the author of the review should have read the book and should only be referring to this book in the review.

I think it's a secondary source.

8 0

3 years ago

If I subtract 20 from my number, then square the result, I get the same answer as if I square my number, then subtract 20 from t

Natasha_Volkova [10]

The value of the unknown number is 10.5.

Let the unknown number = x

When 20 is subtracted from the number and the result is squared which is equal to the square of the unknown number minus 20:

(x - 20)² = x² - 20

<em>expand the equation;</em>

x² - 40x + 400 = x² - 20

<em>collect similar terms together;</em>

x² - x² - 40x = -20 - 400

-40x = -420

$x = \frac{420}{40}\\\\ x = 10.5$

Thus, the value of the unknown number is 10.5.

Learn more about word problem here: brainly.com/question/18336356

7 0

2 years ago