Answer:
0
Step-by-step explanation:
Quadratic equation

The discriminant is the part of the quadratic formula within the square root symbol:
. The discriminant indicates if there are two solutions, one solution, or none.
The discriminant can be positive, zero or negative which determines how roots exist for the given quadratic equation.
So, a positive discriminant tell us that the quadratic has two different real solutions.
A discriminant of zero tell us that the quadratic has two real and equal solutions.
And a negative discriminant tell us that none of the solutions are real numbers.
In this case: 25x^2-10x+1=0
We can see that
a= 25 b=-10 c=1
Using: 
We have 
the answer is zero, so the quadratic has two real and equal solutions
X=-7 AB=-72
steps
since m is a midpoint, AM and MB are congruent so you set the two equations equal to each other, 4x-9=5x-3/3( is this a typo? bc 3/3 is 1)
subtract 4x from both sides m, -8=x-1
add 1 to both sides
x=-7
then plug -7 in for x 4(-7)-8=-36
since the two segments are congruent u do -36 x 2= -72
Here you go enjoy
Have a good rest of your night