2. Example-2
1. Find Decompose(A,B,C) `A=(3,7)`,`B=(-1,2)`,`C=(3,20)`
Solution: Here `vec A=(3,7),vec B=(-1,2),vec C=(3,20)`
Form equation from vectors `vec C = x vec A + y vec B`
So system of linear equations are `3x-1y=3`
`7x+2y=20`
Solution of equations using Elimination methodTotal Equations are `2` `3x-y=3 -> (1)` `7x+2y=20 -> (2)`
Select the equations `(1)` and `(2)`, and eliminate the variable `y`. `3x-y=3` | ` xx 2->` | | `` | `6x` | `-` | `2y` | `=` | `6` | `` | | | + | | `7x+2y=20` | ` xx 1->` | | `` | `7x` | `+` | `2y` | `=` | `20` | `` | | | |
| | | | `` | `13x` | | | `=` | `26` | ` -> (3)` |
Now use back substitution method From (3) `13x=26` `=>x=(26)/(13)=2` From (1) `3x-y=3` `=>3(2)-y=3` `=>-y+6=3` `=>-y=3-6=-3` `=>y=3` Solution using Elimination method. `x=2,y=3`
`x=2,y=3`
So, `vec C=2vec (A) +3vec (B)`
2. Find DECOMPOSE(B,C,A) `A=(1,2)`,`B=(3,1)`,`C=(8,1)`
Solution: Here `vec A=(1,2),vec B=(3,1),vec C=(8,1)`
Form equation from vectors `vec A = x vec B + y vec C`
So system of linear equations are `3x+8y=1`
`x+y=2`
Solution of equations using Elimination methodTotal Equations are `2` `3x+8y=1 -> (1)` `x+y=2 -> (2)`
Select the equations `(1)` and `(2)`, and eliminate the variable `x`. `3x+8y=1` | ` xx 1->` | | `` | `3x` | `+` | `8y` | `=` | `1` | `` | | | − | | `x+y=2` | ` xx 3->` | | `` | `3x` | `+` | `3y` | `=` | `6` | `` | | | |
| | | | | | `` | `5y` | `=` | `-5` | ` -> (3)` |
Now use back substitution method From (3) `5y=-5` `=>y=(-5)/(5)=-1` From (2) `x+y=2` `=>x+(-1)=2` `=>x-1=2` `=>x=2+1=3` Solution using Elimination method. `x=3,y=-1`
`x=3,y=-1`
So, `vec A=3vec (B) -vec (C)`
This material is intended as a summary. Use your textbook for detail explanation. Any bug, improvement, feedback then
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