davidjohn03
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Hi, I've got this far in the Q but i'm unsure how to factor out (a+d) or have I done something wrong ? can someone please help?
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davidjohn03
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(Original post by davidjohn03)
Hi, I've got this far in the Q but i'm unsure how to factor out (a+d) or have I done something wrong ? can someone please help?
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mqb2766
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Use the fact it's singular.
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davidjohn03
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(Original post by mqb2766)
Use the fact it's singular.
I've done that now i got the first set of diagonals multiplied out minus the 2nd pair and set it = 0
I still can't factor out ?
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mqb2766
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(Original post by davidjohn03)
I've done that now i got the first set of diagonals multiplied out minus the 2nd pair and set it = 0
I still can't factor out ?
Can you upload?
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ghostwalker
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(Original post by davidjohn03)
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Your factorisations along the descending diagonal are both incorrect.

E.g. a(a+bc) does not equal a^2+bc
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davidjohn03
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(Original post by mqb2766)
Can you upload?
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mqb2766
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You were closer the first time. Singular means
ad = bc
And when you do M^2, all the elements are quadratics , not cubic as pointed out above.

You know what you want each element to be
a(a+d), b(a+d), c(a+d), d(a+d)
Work towards that.
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davidjohn03
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I am still confused I think I have the correct result now tho Name:  B9BBF6B0-2B31-4AF7-9C15-E1A7B9EABDED.jpg.jpeg
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ghostwalker
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(Original post by davidjohn03)
I am still confused I think I have the correct result now tho Name:  B9BBF6B0-2B31-4AF7-9C15-E1A7B9EABDED.jpg.jpeg
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Not sure what you're doing with those last three lines. Looks as if you're working out the determinant of M^2. Though it's completely by the by.

Taking it from the very top. Your second line of working was good. Now just replace bc with ad in the terms on the descending diagonal. Then factorise as you did in your second post. You can then extract a factor from the matrix and you're done.
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davidjohn03
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Ahhh thank you ! I overthought it
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