Question Bank - Mathematics

Here's the question bank on all the mathematics topics.

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Let r be a root of the equationx2 +2x + 6 = 0.Then the value of the expression (r + 2)(r + 3)(r + 4)(r + 5) is

A.
51
B.
-51
C.
126
D.
-126

Solution:

The correct answer is option 4.Concept:The value r be the root of the equation x2 + 2x + 6 = 0so it will satisfy the, r2+2r+6 =0 ---------(i)r2+2r =-6 ---------(ii)The expression (r + 2)(r + 3)(r + 4)(r + 5)= (r2+5r+6)(r2+9r+20)=(r2+2r+6+3r)(r2+2r+6+7r+14)=(0+3r)(0+7r+14) From (equ i)=3r(7r+14)=21(r2+2r) From (equ ii)=21(-6)=-126Hence the correct answer is -126

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