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5. 2x2 + 5x +2 07. 2= 12x-9x26.2(x2 + 1) = 7x8. 3 (y2 + 1)-Ty9. A two digit number is such that the product of the digits is 20. If 9 issubtracted from the number, the digits interchange their places. FindCBSE 2012the number. |
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Answer» Given :Let the x be th number at units place and y be the number at digits placenumber will be =x+10yReverse number will be 10x+yProduct of digit is 20Therefore,xy=20 -----{1}original number + 9=reverse number9x-9y=9x-y=1-------{2}using formula (x+y)²=(x-y)²+4xy(x+y)²=(1)²+4(20) [ by using equation 1 and 2](x+y)²=1+80=81(x+y)=9-----(3)solve equation 3 and 2x+y=9x-y=1_______by adding, we get,2x=10⇒x=5y=9-5y=4so x and y are 5 and 4so number is x +10y =5 +10x4=5+40=45 ∴Required number is 45 |
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