`a) x^2 + 6x + 9` `b) x^2 + x + 1/4` `a) (2x-5)(x+2) – 2x(x-1) = 15` `a) 2 . 3^x = 162` `1) (-3)/11 + 7/15 + 8/(-11) – (-3)/(

1 bình luận về “`a) x^2 + 6x + 9` `b) x^2 + x + 1/4` `a) (2x-5)(x+2) – 2x(x-1) = 15` `a) 2 . 3^x = 162` `1) (-3)/11 + 7/15 + 8/(-11) – (-3)/(”

1. a) x^2 + 6x + 9

   = x^2 + 2 . x . 3 + 3^2

   = (x+3)^2

   $$

   b) x^2 + x + 1/4

   = x^2 + 2 . x . 1/2 + (1/2)^2

   = (x+1/2)^2

   $$

   a) (2x-5)(x+2) – 2x(x-1) = 15

   => 2x^2 – 5x + 4x – 10 – 2x^2 + 2x = 15

   => x – 10 = 15

   => x = 25

   Vậy x = 25

   $$

   a) 2 . 3^x = 162

   => 3^x = 162 : 2

   => 3^x = 81 = 3^4

   => x = 4

   Vậy x = 4

   $$

   1) (-3)/11 + 7/15 + 8/(-11) – (-3)/(-4) + 9/15

   = ((-3)/11 + 8/(-11)) + (7/15 + 9/15) – 3/4

   = -1 + 16/15 – 3/4

   = -60/60 + 64/60 – 45/60

   = -41/60

   $$

   d) (1 – 2x)^2 + (2x+1)(1-2x)= 18

   => [1^2 – 2 . 1 . 2x + (2x)^2] + [1^2 – (2x)^2]= 18

   => 1 – 4x + 4x^2 + 1 – 4x^2 = 18

   => -4x + 2 = 18

   => -4x = 16

    

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