a) 5 ( x + 2 ) = 9 ( 10 – 2x ) b) ( x + 5 ) ( x – 3 ) + x^2 – 25=0 c) x^4 – 2x^2 – 144x -1295=0

0 bình luận về “a) 5 ( x + 2 ) = 9 ( 10 – 2x ) b) ( x + 5 ) ( x – 3 ) + x^2 – 25=0 c) x^4 – 2x^2 – 144x -1295=0”

1. a. => 5x + 10 = 90 – 18x

       => 5x + 18x = 90 – 10

       => 23x = 80

       => x = 80/23

   b. x^2 – 3x + 5x – 15 + x^2 – 25= 0

   => 2x^2 + 2x – 40 = 0

   => 2( x^2 + x -20) = 0

   => 2 ( x^2 – 4x + 5x -20) = 0

   => (x-4)(2x+5) = 0 

   => x = 4, x = -5/2 

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2. a) 5 ( x + 2 ) = 9 ( 10 – 2x )

   ⇔ 5x+10=90-18x

   ⇔23x=80

   ⇔ x=80/23

   b) ( x + 5 ) ( x – 3 ) + x^2 – 25=0

   ⇔x²+2x-15+x²-25=0

   ⇔ 2x²+2x-40=0

   ⇔x²+x-20=0

   ⇔(x+5)(x-4)=0

   ⇔x=-5

       x=4

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