Can the sum or difference on two quadratic functions be a linear function?

Yes

Step-by-step explanation:

e.g if  x^2+y=7 and x^2+3y=9  are two quadratic functions, their difference is a linear function i.e. -2y=-2.

step-by-step explanation:

the original amount doesn't ''re just looking for the time it takes for 1/2 of the substance to we have

(1/2) =)     take the ln   of both sides

ln (1/2)   = )   and we can write

ln(1/2) = ) lne     and lne   = 1     so we have

ln(1/2) = -.1092t     divide both sides by -.1092

t = ln(1/2)/-.1092 = about 6.347 days = about 6.3 days (rounded)