1. Solve Equations 2x+5y=21,x+2y=8 using Cramer's Rule method

Solution:
The equations can be expressed as
`2x+5y-21=0`

`x+2y-8=0`

Use Cramer's Rule to find the values of x, y, z.
`(x)/D_x=(-y)/D_y=(1)/D`

`|D_x|`

=

`5`   `-21`   `2`   `-8`

`=5 × (-8) - (-21) × 2`

`=-40 +42`

`=2`

`|D_y|`

=

`2`   `-21`   `1`   `-8`

`=2 × (-8) - (-21) × 1`

`=-16 +21`

`=5`

`|D|`

=

`2`   `5`   `1`   `2`

`=2 × 2 - 5 × 1`

`=4 -5`

`=-1`


`(x)/D_x=(-y)/D_y=(1)/D`

`:. (x)/2=(-y)/5=(1)/-1`

`:. (x)/2=(1)/-1,(-y)/5=(1)/-1`

`:. x=(2)/(-1),y=(-5)/(-1)`

`:. x=-2,y=5`

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