What is the answer to 9/9x - 5/10x + 1/9x

[10 points, algebra 2]according to my answer key the restrictions are -1 and 4. but why not positive 1?

Someone answer asap for ! a ball is rolled down a ramp. the height, f(x), in meters, of the ball x seconds after it is released is modeled by the function f(x) = x²- 10x + 25 for all values of x from 0 to 5. which statement about the ball is true? a. the maximum height of the ball is 5 meters b. the height of the ball increases from 0 to 5 meters above the ground. c. the ball has traveled 5 meters when it reaches the bottom of the ramp. d. the ball has been traveling for 5 seconds when it reaches the bottom of the ramp

Idon't get undoing if its pass adding and subtracting so can someone ? x-2 over 5 = 18