## Diana.xL one year ago http://prntscr.com/8icsqs

1. Diana.xL

@hartnn

2. hartnn

16 is the square of which number?

3. Diana.xL

4

4. hartnn

yeah so we have $$x^2-4^2$$ use the formula $$\Large a^2-b^2 = (a+b)(-b)$$ so $$x^2-4^2 = ...?$$

5. Diana.xL

6. imqwerty

no

7. zzr0ck3r

HINT: this is the exact same question as last time

8. Diana.xL

its b

9. imqwerty

u can write that as $x^2-4^2$ nd then use the identity$a^2-b^2=(a+b)(a-b)$

10. zzr0ck3r

correct

11. Diana.xL

Thanks!

12. zzr0ck3r

$$x^2-16=0\implies x^2=16\implies x=\pm\sqrt{16}=\pm4$$

13. zzr0ck3r

remember, that when you induce the square you get two answers.

14. zzr0ck3r

what I mean by that is that when you have x^2=16 you get two answers, but if I ask you what sqrt(16) is, then it is 4

15. Diana.xL

oh ok ty