19)
solve the quadratic equation x2 − 18x + 81 = 64 for x.

a)
x = 17 or x = 1

b)
x = 11 or x = −5

c)
x = 9 or x = −8

d)
x = 2 or x = 9

{1, 17}

Step-by-step explanation:

x2 − 18x + 81 = 64 can be rewritten as x² - 18x + 81 = 64.

Next, x² - 18x + 81 can be rewritten as (x - 9)²

so that we now have:

(x - 9)² = 64.

Taking the sqrt of both sides, we get

x - 9 = ± 8

Then one root is x = 9 + 8 = 17, and the other is x = 9 - 8 = 1.

{1, 17} is the set of roots

-14

step-by-step explanation:

2x2 – 2(x+4)

=2x2-2（5+4）

=4-2×9

=4-18

=-14

4.08%

step-by-step explanation: