<h3>
Answer:</h3>
18. x = y = -3
21. y was substituted into the wrong equation. The solution is (x, y) = (2, 1).
<h3>
Step-by-step explanation:</h3>
18. Adding y to the first equation transforms it to ...
... x = y
Then you can substitute for either variable in the second equation.
... 2y -5y = 9 . . . . . substitute for x
... -3y = 9 . . . . . . . . simplify
... y = -3 . . . . . . . . . divide by the coefficient of y
.. x = -3 . . . . . . . . . x and y have the same value
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21. The first equation is being used to find an expression for y in terms of x. If you substitute that expression back into the same equation, it will tell you nothing you didn't already know. (Here, it is telling you 5 = 5.) The expression is only useful if you <em>substitute it into a different equation</em>. Here, it needs to be substituted into the second equation:
... <u>Step 2</u>: 3x -2(-2x+5) = 4 ⇒ 7x -10 = 4 . . . . . substitute for y in the second eqn
... <u>Step 3</u>: 7x = 14 . . . . . add 10
... <u>Step 4</u>: x = 2 . . . . . . . divide by 7
... <u>Step 5</u>: y = -2·2 +5 = 1 . . . . . find the value of y from x using the expression from step 1. Now, you know the solution is (x, y) = (2, 1).
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The attached graph shows the solution to the problem of 21.
Answer:
C
Step-by-step explanation:
If
then

Substitute them into the equation 

Given
then

Hence,

Answer:you need to know the amount of students I think
Step-by-step explanation:
Um do you want that simplified you need to add more information or something
We can find this using the formula for arc length (where
is the radius of the circle and
is the central angle in radians):

In our problem, we are given
. This means that:

The measure of the angle is 1.5.