## LilVeroDez13 3 years ago Counterexample problem.. jus want to know if its right. Thanks!

1. LilVeroDez13

x = 1

2. Emah

that looks right:)

3. LilVeroDez13

thanks! :)

4. TuringTest

it's not right

5. TuringTest

what would happen if you plugged in x=1 ? you get\[x^2\ge1\implies x\ge1\]\[1^2\ge1\implies1\ge1\]where is the falsehood here?

6. myininaya

I agree with @TuringTest 1 does equal 1.

7. LilVeroDez13

ohh yeah.. it wouldnt b false.

8. Emah

but its saying OR equal to

9. TuringTest

and it is equal, so it's true

10. LilVeroDez13

@Emah yeahh thats true.. i dont see another answer that works

11. TuringTest

try each one individually

12. Emah

oh oops i sdidnt see the part that said couterexample:( sorry

13. LilVeroDez13

ohh its okk

14. TuringTest

what do you get when you plug in x=2\[x^2\ge1\]\[x\ge1\]are both still true?

15. LilVeroDez13

i get that its false

16. TuringTest

which part is false?

17. LilVeroDez13

first part

18. TuringTest

\[2^2\ge1\]is not true you say?

19. LilVeroDez13

Im confused

20. TuringTest

we need to find an example where the first part is true, and the second part is false to disprove the statement

21. TuringTest

\[2^2=4\]and four is greater than one, so \[x^2\ge1\]is true for x=2

22. TuringTest

what about the other part, is\[2\ge1\]?

23. LilVeroDez13

its true because 2 is greater tha 1

24. TuringTest

right, so both statements are true for x=2, so this is not a counterexample

25. TuringTest

what about for x=-3 is\[x^2\ge1\]and is\[x\ge1\]?

26. LilVeroDez13

first one is 9 > 1 (true) second one is 3 > 1 (true too)

27. LilVeroDez13

so than its 1/4 (:

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