Question

Coordinates of C and D are (-14 , 6) and (x , 13) respectively.Given x is a positive integer and the distance CD is 25 units.Find the value of x.​

Answer 1

10

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.