Q6. Given

the vertex is in between the two zeros; it's

which we know from the quadratic formula is the midpoint between the zeros.
We get a negative x coordinate when a and b have the same signs. Let's go through the choices.
-3 and -7 have the same sign, negative x, CHECK
different signs, nope
different signs, nope
same sign, CHECK
1st and 4th choice.
Q7.
The correct first step of evaluating the polynomial at x=3/4 is to substitute 3/4 for x, first choice.