vera_ewing one year ago Math question

1. vera_ewing

2. welshfella

differentiate and equate to zero to find the turning points

3. Michele_Laino

furthermore the first derivative of your function is: $f'\left( x \right) = 9{x^2} - 16$

4. anonymous

円の円周は直径として直接変化します。円は60フィートの直径と188.4フィートの円周を持っています。 15フィートの直径とする円の円周は何ですか？ 47.1フィート 7.5フィート 57.1フィート

5. Michele_Laino

your function is an increasing function if the subsequent condition holds: $9{x^2} - 16 > 0$

6. Michele_Laino

7. vera_ewing

9x^2-16>0 9x^2>0+16 9x^2>16 x>4/3

8. ribhu

not this way...

9. ribhu

find two solution.. square root is written with positive and negative sign...

10. freckles

what's up with those subscripts being x?

11. Michele_Laino

we can rewrite that inequality as below: $\left( {3x - 4} \right)\left( {3x + 4} \right) > 0$ so the starting inequality is equivalent to the subsequent two systems of inequalities: $\left\{ \begin{gathered} 3x - 4 > 0 \hfill \\ 3x + 4 > 0 \hfill \\ \end{gathered} \right.,\quad \left\{ {\begin{array}{*{20}{c}} {3x - 4 < 0} \\ {3x + 4 < 0} \end{array}} \right.$ please solve them

12. welshfella

you could have also have found the turning points and their nature and drawn a rough graph which might have looked like |dw:1444420588420:dw|

13. welshfella

then the increasing/ decreasing intervals can be seen from the graph.

14. vera_ewing

Ok so it's D?

15. Michele_Laino

i'm sorry option D is a wrong option

16. anonymous

what is 9+9

17. vera_ewing

Ok so it has to be B?

18. Michele_Laino

correct!

19. vera_ewing

Ok, thank you Michele!!!

20. Michele_Laino

:)