Bonjour Boa87,
Only for iMac, Macbook … not available for iPad :
I use MathType 6.7 which works perfectly with iWork, much better than Grapher equation editor. Website :
http://www.dessci.com/en/products/mathtype_Mac/
It's free for 30 days, then it becomes "Lite MathType" same as Equation Editor from Microsoft Word.
Using MathType allows you to edit math expressions in a Pages text.
Explanations on DESSCI FAQ website (English). http://www.dessci.com/en/products/mathtype_mac/faqs.htm at FAQ nr 4.
Au revoir,
YB24