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ECAT and MCAT Preparation: Post your doubts here!
- Thread starter smzimran
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Can you post the formula for the first three ?
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Post it!
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The answer is -6
You see in such questions, you can end up wasting most of your time if you dont think wisely. 1st expand by 1st column. Since there is only one non zero entry in it, it'll be easier. After expansion you'll get a 4x4 determinant.
now expand by 4th row, because of the same reason (only 1 non zero entry)
Now that you have a 3x3 determinant, expand by 1st column. I guess you can do the rest
And final step, -2 x 3 = -6
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Lol no. You cant afford to skip Conics. The 7th chapter is not that important though.
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Oh you talking about chemistry? yeah nobody does those two chapters.
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uhm could you explain that again, didn't quite get itThe answer is -6
You see in such questions, you can end up wasting most of your time if you dont think wisely. 1st expand by 1st column. Since there is only one non zero entry in it, it'll be easier. After expansion you'll get a 4x4 determinant.
now expand by 4th row, because of the same reason (only 1 non zero entry)
Now that you have a 3x3 determinant, expand by 1st column. I guess you can do the rest
And final step, -2 x 3 = -6
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Ah it's really hard to explain maths like this. Anyway i'll try again.uhm could you explain that again, didn't quite get it
Do you know how to expand a 3x3 determinant? This is the same thing. When you expand a 3x3 determinant, you are actually converting it into a lesser order matrix ,i.e a 2x2 matrix which is then solved by 'ad-bc' formula.
Now the given determinant was of 5x5 order. You expand it/convert it into a lower order determinant, i.e 4x4
You have got more than 1 4x4 determinants corresponding to the number of elements in that row or column. Now the technique was that if we use such a row or column for expansion which has only one non-zero entry, we get only 1 4x4 determinant. Had we considered a row or a column having more than 1 non zero entries, there would have been more than 1 4x4 determinants, which would have made the problem confusing.
Now using that 1 4x4 determinant, we again consider a row or a column for expansion which would give only one lesser order i.e, 3x3 determinant.
Then we expand the 3x3 determinant and solve it by ad-bc. I hope that helped