Use cramer's rule to find x in the system of equations below.

2x − 3y = 17

5x + 4y = 8

x = 4 , y = -3

Step-by-step explanation:

Going by the Cramer's rule , we first determine the determinant by dealing with only  the coefficients of x and y in the 2 x 2 matrix.

2x  -  3y = 17

5x  + 4y = 8

2        -3

5         4,   going by the rule now, we now have

(2 x 4) - (5 x -3)

8 + 15

= 23.

Now to find the value of x , replace the constants with the coefficient of x and divide by he determinants.

 17        -3

 8          4

2           -3

5            4

( 17 x 4 ) - ( 8 x -3 )

         23

     =  68 + 24

              23

    =       92/23

    =           4.

 x =   4

Now  to find y, just repeat the process by replacing the coefficient of y with the constants.

2        17

5        8

2        -3

5         4

( 2 x 8 ) - ( 5 x 17 )

            23

       16 - 85

          23

  =  -69/23

  =   -3

y =  -3.

check

substitute for the values in any of the equations above.

2(4)  - 3(-3)

8  + 9

= 17

the value of v.w= -12.

step-by-step explanation:

we are given three vector r,v and w as:

r = < 5, -5, -2> ; v = < 2, -8, -8> ; w = < -2, 6, -5>

we know that r,v and w could also be represented as:

r=5i-5j-2k

v=2i-8j-8k

and w= -2i+6j-5k

where i,j and k are the unit vectors of x,y and z-axis respectively.

also we know that it has the following property:

i.i=1 ; j.j=1; k.k=1

and i.=j.i=i.k=k.i=j.k=k.j=0

i.e. when we multiply two vectors or we find it's dot product we need to only multiply the components of x coordinates with each other; y with each other and z with each other.

hence, v.w= (2i-8j- -2i+6j-5k)

                  = 2×(-2)+(-8)×(6)+(-8)×(-5)

                  = -4-48+40

                  = -12

hence, v.w= -12

s

step-by-step explanation: