The value of x is such that matrix product ⎡⎢⎣2070101−21⎤⎥⎦⎡⎢⎣−x14x7x010x−4x−2x⎤⎥⎦ equals an identity matrix. Then the value of 20x is
A
4
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B
5
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C
1
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D
7
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Solution
The correct option is A 4 ⎡⎢⎣2070101−21⎤⎥⎦⎡⎢⎣−x14x7x010x−4x−2x⎤⎥⎦=⎡⎢⎣5x00010010x−25x⎤⎥⎦=⎡⎢⎣100010001⎤⎥⎦ (given) Comparing elements we get, ⇒5x=1,10x−2=0,∴x=15