Question

How do I solve this using substitution?
y=5x+2
y=y^2+x^2=40,000

Answer 1

so where are you stuck?
what have you tried?

Answer 2

Pretty much the first step, when I combine them I'm not sure where to go afterwards

Answer 3

there's no like terms to combine
anyways, can you please check your 2nd equation?
there are 2 = signs in it :P
somethin's not correct...

Answer 4

I was supposed to come up with the first equation myself so maybe thats the problem... and oh wow sorry I meant y^2+x^2=40000

Answer 5

And when I said combine I mean substitute one of the equations into the other, unless I'm doing this whole lesson wrong :P

Answer 6

no, you're not :)

thats the correct approach!
plug in
y= 5x+2

in 2nd equation,
what u get?

Answer 7

So would that get rid of the y^2?

Answer 8

it will get rid of y
and you will have equation only in x !

Answer 9

\(\Large (5x+2)^2 + x^2 = 40000\)

can you solve that?

Answer 10

I'm so confused, sorry! Are you saying there will be no y's in the new equation?

Answer 11

ofcourse!
because you replaced the 'y' with 5x+2

Answer 12

Ohh I see! thats what I had written down but I thought it wasn't right :P I'll try to solve it

Answer 13

So I'd simplify the (5x+2)^2 first, right? Which would be 25x^2+20x+4?

Answer 14

correct
now combine like terms

Answer 15

45x^2+4?

Answer 16

x^2 and x are not like terms!

Answer 17

\(25x^20x+4+x^2 =40000\)

are u sure its 40000? :P

Answer 18

***
\(25x^2+20x+4+x^2 =40000\)

Answer 19

Yes it is :P

Answer 20

Do I subtract 4?

Answer 21

no
\((25+1)x^2 +20x + (4-40000) = 0\)

Answer 22

thats how you combine like terms

Answer 23

\(26x^2+20x-39996=0\)
try to solve that

Answer 24

+39996 on both sides?

Answer 25

won't help
thats a quadratic equation
know any method to solve a quadratic equation?

Answer 26

Ah I figured out what I was doing wrong, thank you for helping! :)