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♦ (X+2)³= x(x²-1) ♦
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Answer:
Given :
( x + 2 )³ = x ( x² - 1 )
⇒ ( x + 2 )³ = x³ - x
We know that ( a + b )³ = a³ + b³ + 3 ab ( a + b )
⇒ x³ + 2³ + 3 × 2 × x ( x + 2 ) = x³ - x
⇒ x³ + 8 + 6 x ( x + 2 ) = x³ - x
Cancel the x³ from both sides :
⇒ 8 + 6 x ( x + 2 ) = - x
⇒ 8 + 6 x² + 12 x + x = 0
⇒ 6 x² + 13 x + 8 = 0
The above equation when compared with ,
a x² + b x + c = 0 gives :
a = 6
b = 13
c = 8
Step-by-step explanation:
First of all open all the brackets . Cubing the LHS will require us to use the identity of ( a + b )³ .
After that we can reduce the equation to a quadratic equation .
The solutions of quadratic equation can be easily found by the quadratic formula .
Here the square root of a negative number is an imaginary number and is denoted by i .
Note that roots are complex and not real !
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