My Math Forum Determinant related question!

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 November 27th, 2016, 01:08 PM #1 Member   Joined: Jan 2016 From: / Posts: 36 Thanks: 1 Determinant related question! So I have got this problem. I'd be happy if someone can solve it for me, i'm currently in a big rush and it's the only one that I've got left to complete my assignment My assignment is : Find real number t such that : $\begin{vmatrix} 1 &2 & 3 &4 \\ t+1 &2&t+3 &4 \\ 1 &3+t &4+t &5+t \\ 1 &-3 &-4 &-5 \end{vmatrix} =0$ The results should be : t1 = -1 and t2 = 0 I know I should understand and i tried but can't figure it out and i'm really in a rush! Help me if you know how to solve!
November 27th, 2016, 01:11 PM   #2
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Quote:
 Originally Posted by SuperNova1250 So I have got this problem. I'd be happy if someone can solve it for me, i'm currently in a big rush and it's the only one that I've got left to complete my assignment My assignment is : Find real number t such that : $\begin{vmatrix} 1 &2 & 3 &4 \\ t+1 &2&t+3 &4 \\ 1 &3+t &4+t &5+t \\ 1 &-3 &-4 &-5 \end{vmatrix} =0$ The results should be : t1 = -1 and t2 = 0 I know I should understand and i tried but can't figure it out and i'm really in a rush! Help me if you know how to solve!
If two lines are the same then the determinant is 0, right? Look at rows one and two...

-Dan

 November 27th, 2016, 01:14 PM #3 Member   Joined: Jan 2016 From: / Posts: 36 Thanks: 1 TopSquark, thanks man for the fastest response ever! Yeah that sure does make sense but i'm not sure if that is going to be enough to put down on the paper. Isn't there some step by step solution i can get? Thanks again!
 November 27th, 2016, 01:37 PM #4 Member   Joined: Jan 2016 From: / Posts: 36 Thanks: 1 Can anyone help?
 November 27th, 2016, 03:25 PM #5 Math Team     Joined: May 2013 From: The Astral plane Posts: 1,797 Thanks: 715 Math Focus: Wibbly wobbly timey-wimey stuff. Well, if you want a rigorous method to do the problem expand out the determinant and solve for t! It's a 4 x 4 so it isn't so bad. I had thought you were to exploit some basic theorems to hone in on the two solutions. -Dan

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