Answer:
10
Step-by-step explanation:
1) The vector CD is equal to (X-(-14); 13-6)= (x+14; 7)
2) The module of the vector CD is equal to diatance CD=25. It is equal to
sqrt ((x+14)(x+14)+7*7) from the formula of module (with coordinates).
25= sqrt ((x+14)(x+14)+7*7)
625= (x+14)*(x+14)+49
625= x^2+28x+196+49
X^2+28X-380=0
a=1 b=28 c=-380
D= b*b-4ac= 28*28-4*1*(-380)= 784+1520= 2304
sqrt D= sqrt2304=48
x1= (-28-48)/2= -38
x2= (-28+48)/2= 10
But x1<0 it is negative and it is not suitable, x2>0 it is positive, so answer is 10.
