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i dont know how to use cramers rule

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2x-4y=-18

4x-2y=-30

asked Nov 21, 2013 in ALGEBRA 2 by abstain12 Apprentice
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1 Answer

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Given equations are 2x-4y = -18 and 4x-2y = -30

Carmers rule is AX = B

A is an coefficient matrix, x is a varible matrix and B is a constant matrix.

Convert the equations into matrices form.

open parentheses table row 2 cell minus 4 end cell row 4 cell minus 2 end cell end table close parentheses open parentheses table row x row y end table close parentheses equal open parentheses table row cell minus 18 end cell row cell minus 30 end cell end table close parentheses

d e t A equal minus 4 plus 16 equal 12

d e t A 1 equal open parentheses table row cell minus 18 end cell cell minus 4 end cell row cell minus 30 end cell cell minus 2 end cell end table close parentheses equal 36 minus 120 equal minus 84

d e t A 2 equal open parentheses table row 2 cell minus 18 end cell row 4 cell minus 30 end cell end table close parentheses equal minus 60 plus 72 equal 12

x equal fraction numerator d e t A 1 over denominator d e t A end fraction equal fraction numerator minus 84 over denominator 12 end fraction equal minus 7

y equal fraction numerator d e t A 2 over denominator d e t A end fraction equal 12 over 12 equal 1

The solution of given equations x = -7,y = 1

answered Nov 22, 2013 by william Mentor

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