Question #104593

Use Cramer’s rule to solve

x+2y+z=5

2x+2y+z=6

x+2y+3z=9

Expert's answer

D=∣121221123∣=6+2+4−2−2−12=−4D=\begin{vmatrix} 1 & 2 & 1\\ 2 & 2 & 1\\ 1 & 2 &3 \end{vmatrix}=6+2+4-2-2-12=-4

Dx=∣521621923∣=30+18+12−18−36−10=−4D_x=\begin{vmatrix} 5 & 2&1 \\ 6& 2&1\\ 9&2&3 \end{vmatrix}=30+18+12-18-36-10=-4

Dy=∣151261193∣=18+18+5−6−30−9=−4D_y=\begin{vmatrix} 1&5&1\\2&6&1\\1&9&3 \end{vmatrix}=18+18+5-6-30-9=-4

Dz=∣125226129∣=18+20+12−10−36−12=−8D_z=\begin{vmatrix} 1&2&5\\2&2&6\\1&2&9 \end{vmatrix}=18+20+12-10-36-12=-8

x=Dx/D=(−4)/(−4)=1;x=D_x/D=(-4)/(-4)=1;

y=Dy/D=(−4)/(−4)=1;y=D_y/D=(-4)/(-4)=1;

z=Dz/D=(−8)/(−4)=2.z=D_z/D=(-8)/(-4)=2.

Answer:

x=1;y=1;z=2.x=1; y=1; z=2.


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