Question

What are the x-coordinates of the solutions to this system of equations
A. -4 and 0
B. 4 and 0
C. -3 and -5
D. 3 and -5

Answer 1

X^2+y^2=25
Y=2x-5

Answer 2

Ok, @phi may be able to help you on this

Answer 3

Ok thanks!

Answer 4

No problem! Welcome to OpenStudy!

Answer 5

Thanks!

Answer 6

you can solve the system, or you can test the choices.

to test choice A (for example)
start with x=-4 and use the second equation to find y
can you do that ?

Answer 7

I'm not sure what to do

Answer 8

At allll

Answer 9

start with
y=2x-5

if x= -4 , what is y ? do find out , erase the "x", and put in -4
(remember 2x means 2 times x)
can you do that ?

Answer 10

Y=-13 ?

Answer 11

Y=0

Answer 12

y=2x-5
with x=-4, we get
y= 2* (-4) -5
y= -8 -5 (order of operations means we do multiply first)
y= -13

this mean when x=-4 y= -13
now we test if this pair works in the first equation (which is a circle by the way)
(-4)^2 + (-13)^2 = 25
I don't need a calculator to know that -13*-13 is bigger than 100 (because 10*10 is 100)
and -4*-4 is 16. we will not get 25.

all of that means x=-4 is not part of the answer. so choice A is not the answer

Answer 13

now let's test choice B
let x=4
and find y, using y=2x-5
can you find y ?

Answer 14

replace the x with 4 in
y=2x-5
and simplify

Answer 15

Y=3

Answer 16

ok. so for choice B, we have x=4, y=3
can you use those numbers in the first equation
\[ x^2 + y^2 = 15 \]
?

Answer 17

No 16+9 =15 it doesn't work

Answer 18

oh, I typed in the first equation wrong.

Answer 19

can you use the correct equation and try again ?

Answer 20

X^2+y^2=25