Why do you need to change the signs in -x^2+6x+m=0 ?

It isn't necessary but having a positive coefficient for makes things like completing the square and factoring easier.

if x decreases by 4 then y increases by 10

step-by-step explanation:

a) 0.25x times 3. (could be wrong on equation.)

b) 2.25 pound of dark chocolate. (can i eat all the chocolate? plz? anyway, again, could be wrong, but i hope im right. all the chocolate together should be 5.25 pounds)

have a good day!