I am confused by this problem because of all of the minuses. The problem is:
. . .y = -(x - 5)^2 + 11
I worked it by using FOIL:
. . .(x - 5)(x - 5)
. . .x^2 - 10x + 25
But because of the "minus" in front, I put:
. . .-x^2 + 10x - 25
Then I used the formula for the vertex, and put x = -b/(2a), which I did as:
. . .-(10) / (2(-1))
. . .-[(10) / (-2)]
. . .-(-5)
...or x = 5. Then I put x back into the expression:
. . .(-5)^2 + 10(5) - 25 + 11
This worked out would be y = 39, so the vertex is (5, 39).
. . .y = -(x - 5)^2 + 11
I worked it by using FOIL:
. . .(x - 5)(x - 5)
. . .x^2 - 10x + 25
But because of the "minus" in front, I put:
. . .-x^2 + 10x - 25
Then I used the formula for the vertex, and put x = -b/(2a), which I did as:
. . .-(10) / (2(-1))
. . .-[(10) / (-2)]
. . .-(-5)
...or x = 5. Then I put x back into the expression:
. . .(-5)^2 + 10(5) - 25 + 11
This worked out would be y = 39, so the vertex is (5, 39).