Answer: 28
Step-by-step explanation: you have to add 21 + 7 because your counting up from -7 to 21
The expression that is not a variation of the Pythagorean identity is the third option.
<h3>
What is the Pythagorean identity?</h3>
The Pythagorean identity can be written as:

For example, if we subtract cos^2(x) on both sides we get the second option:

Which is a variation.
Now, let's divide both sides by cos^2(x).

Notice that the third expression in the options looks like this one, but the one on the right side is positive. The above expression is in did a variation of the Pythagorean identity, then the one written in the options (with the 1 instead of the -1) is incorrect, meaning that it is not a variation of the Pythagorean identity.
Concluding, the correct option is the third one.
If you want to learn more about the Pythagorean identity, you can read:
brainly.com/question/24287773
Answer:
(2x+1)(1) = 84. 2x+1= 84. 2x = 83.
Step-by-step explanation:
Minus 12x both sides
0=5x^2-12x+9
use quadratic formula
for 0=ax^2+bx+c
x=
given
5x^2-12x+9
a=5
b=-12
c=9
remember: i=√-1
Using Pythagorean, a^2 + b^2 = c^2
16 +x^2 = 36.69
Then subtract the 16 from 36.69, which is 23.69
And finally take the square root of that, giving you 4.87