Question

Solve the system by the substitution method. Show your work.

2y - x = 5
x2 + y2 - 25 = 0
my answer:
x:
2y - x = 5
2y - 5 = x
so x = 2y - 5
-Plug this into 2nd equation:

(2y - 5)² + y² - 25 = 0

-Use FOIL to solve the (2y - 5)² part:
(2y - 5)(2y - 5)
4y² - 10y - 10y + 25
4y² - 20y + 25

So :
4y² - 20y + 25 + y² - 25 = 0

Which can be simplified to:
4y² + y² - 20y = 0

4y² + y² - 20y = 0
y(4y + y - 20) = 0
So, because of the 0 multiplication rule,
y=0
x= -5 (plug in y=0 to original equations:
2y - x = 5
2(0) - x = 5, so x= -5)

(-5,0)

Answer 1

@hartnn my teacher said incomplete

Answer 2

@Michele_Laino

Answer 3

@master50777

Answer 4

ill be back after lunch

Answer 5

y(4y + y - 20) = 0

so, y = 0
or
4y+y-20 = 0

Answer 6

5y -20 = 0
y =4

Answer 7

when y =4, find x

Answer 8

5y-20=0
5(4)-20=0
0=0
@hartnn

Answer 9

x = 2y -5
when y=4

x = 8-5 =3

Answer 10

is my work correct? and should i add to my previuos answer?

Answer 11

yes, add that to your previous answer

Answer 12

so your final 2 points are
\(\Large (-5,0) \\ \Large (3,4)\)