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Algebra ->  Matrices-and-determiminant -> SOLUTION: <img src="https://screenshotscdn.firefoxusercontent.com/images/ae16e853-679d-4e8c-a3b3-e4e1121fae1a.png">       Log On


   

Question 1138047:
Answer by MathLover1(20850) About Me  (Show Source):
You can put this solution on YOUR website!

matrix%283%2C3%2C2%2Cx%2C1%2C-3%2C1%2C0%2C2%2C1%2C4%29=39
The determinant is:
if you have
matrix%283%2C3%2Ca%2Cb%2Cc%2Cd%2Ce%2Cf%2Cg%2Ch%2Ci%29, then
determinant=+a%28ei+-+fh%29+-+b%28di+-+fg%29+%2B+c%28dh+-+eg%29=39
in your case a=2, b=x,c=1,d=+-3,e=1,f=0,g=2,h=1,i=4
so, you have
2%281%2A4+-+0%2A1%29+-+x%28-3%2A4+-+0%2A2%29+%2B+1%28-3%2A1+-+1%2A2%29=39
2%284+%29+-+x%28-12+%29+%2B+1%28-5%29=39
8++%2B12x+-5=39
12x%2B3=39
12x=39-3
12x=36
x=3