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Question

p(x) is a polynomial such that p(x)= (x-a)(x+10) + 1, a is not equal to 0. 'a' attains integral values for integral roots of the above polynomial. what is the sum of all posible valueesof 'a'??

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Solution

Consider the following polynomial. p(x)=x-ax+10+1 , a0 aZ (non zero Integers)Write the above polynomial in general form. p(x)=x-ax+10+1 =x2+10x-ax-10a+1 =x2+10-ax+1-10aFor a=1, 2, 3, 4, 5, .... the corresponding polynomials are p(x)=x2+9x-9 , a=1 p(x)=x2+8x-19, a=2 p(x)=x2+7x-29, a=3 p(x)=x2+6x-39, a=4 p(x)=x2+5x-49, a=5 If α and β are roots of the above equations.Then it implies that, α + β=9, α β=-9 ,a=1 α + β=8, α β=-19 ,a=2 α + β=7, α β=-29 ,a=3 α + β=6, α β=-39 ,a=4 α + β=5, α β=-49 ,a=5Note that no integral values of α and β satisfy the above relations.Hence the roots are not integral values for a=1, 2, 3, 4, 5, ....For a=-1, -2, -3, -4, -5, .... the corresponding polynomials are p(x)=x2+11x+11 , a=1 p(x)=x2+12x+21, a=2 p(x)=x2+13x+31, a=3 p(x)=x2+14x+41, a=4 p(x)=x2+15x+51, a=5 If α and β are roots of the above equations.Then it implies that, α + β=11, α β=11 ,a=1 α + β=12, α β=21 ,a=2 α + β=13, α β=31 ,a=3 α + β=14, α β=41 ,a=4 α + β=15, α β=51 ,a=5Again, note that no integral values of α and β satisfy the above relations.Such α and β does not exist.Hence the roots are not integral values for a=-1, -2, -3, -4, -5, ....Therefore, there does not exist any integral value of "a" for which the given equation has integral roots

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