## anonymous one year ago y = −x^2 + 4 y = 2x + 1 How would you solve by elimination or substitution?

1. rvc

we have : $\rm y=-x^2+4~ and ~y=2x+1$

2. anonymous

yes, I don't get how you would solve them though

3. rvc

so we have two values for y

4. rvc

we can put any of those

5. anonymous

like $-x^2+4=2x+1$

6. rvc

yes

7. rvc

now solve further :)

8. anonymous

but how would you subract them. Thats what im stuck on.

9. rvc

here it is : $\rm 2x+1+x^2-4$

10. anonymous

that is what y equals then right?

11. rvc

no since when we solve the equation we are left only with x. then we will put the value of x in any one of the original equation to find the value of y

12. anonymous

Im really stuck then .. how would you find what x and y are?

13. rvc

here it is : $\sf x^2+2x-3=0$

14. rvc

we have to solve the quadratic equation

15. anonymous

I get x = 1, -3

16. rvc

yep now put one value at a time in either : y = 2x+1 or y=-x^2+4

17. anonymous

Thank you :)

18. rvc

Thank you All the best :)