For b...

Algebra Level 2

If x 2 x^{2} + ( a + 1 ) x (a+1)x + a a = x 2 x^{2} + b x bx - 6 6 , find b b .


The answer is -5.

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2 solutions

Christian Daang
Jan 15, 2015

Solution:

We know that the given equation above is equal to:

( x + 1 ) (x+1) * ( x + a ) (x+a) = x 2 + b x 6 x^{2} + bx - 6

By using common sense, a a = 6 -6

So,

x 2 5 x 6 x^{2} - 5x - 6 = x 2 + b x 6 x^{2} + bx - 6

t h e r e f o r e , therefore,

b = 5 b = -5 a n s . ans.

I do the same way :D

Felix HG - 6 years, 4 months ago

No need to use common sense too.

From LHS, we get x= -1 and x= -a

Take x= -1 so as to eliminate 'a'

Then,

=> (-1+1)(-1+a) = (-1)^2 + (-1)b - 6

=> 0 = 1-b-6

=> b= -5

Vasudev Chandna - 6 years, 2 months ago
. .
May 14, 2021

x 2 + ( a + 1 ) x a = x 2 + b x 6 x 2 x 2 + ( a + 1 b ) x + a + 6 = 0 ( a + 1 b ) x + a + 6 = 0 a = 6 ( 6 + 1 b ) x = 0 ( 5 b ) x = 0 5 b = 0 b = 5 x ^ { 2 } + ( a + 1 )x a = x ^ { 2 } + bx - 6 \rightarrow x ^ { 2 } - x ^ { 2 } + ( a + 1 - b )x + a + 6 = 0 \rightarrow ( a + 1 - b )x + a + 6 = 0 \rightarrow a = -6 \rightarrow ( -6 + 1 - b )x = 0 \rightarrow ( -5 - b )x = 0 \rightarrow -5 - b = 0 \rightarrow b = -5 .

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