The steps to derive the quadratic formula are shown below:
step 1
ax2 + bx + c = 0
step 2
ax2 + bx = − c
step 3
x2 +
step 4
x2 +
step 5
x2 +
step 6
step 7
step 8
x = −
step 9
x =
which of the following is the first incorrect step? (1 point)
step 4
step 6
step 7
step 8

So the first thing we do is to multiply the top equation by 3. the reason i want to do this is i notice there will be a 6y on both equations and can possibly add/subtract them. so we get 6y = -3x + 27. adding that and the second equation we get 6x = 27-15 which is 12. divide by 6 and we get 2. ∴ x = 2. substituting 2 into the first equation we get 2y = -2 + 9 which is 7. divide by 2 and we get 7/2. ∴ y = 7/2, x = 2.