a) 0,125 ( a + 2)^3 – 1 b) -9a^2 +12ab – 4b^2

2 bình luận về “a) 0,125 ( a + 2)^3 – 1 b) -9a^2 +12ab – 4b^2”

1. Giải đáp:

    a)

   0,125.(a+2)^{3}-1

   =[0,5.(a+2)]^{3}-1^{3}

   =(0,5a+1)^{3}-1^{3}

   =[(0,5a+1)-1].[(0,5a+1)^{2}+(0,5a+1).1+1^{2}]

   =(0,5a+1-1).{[(0,5a)^{2}+2.0,5a.1+1^{2}]+0,5a+1+1]}

   =0,5a.(0,25a^{2}+a+1+0,5a+2)

   =0,5a.(0,25a^{2}+1,5a+3)

   b)

   -9a^{2}+12ab-4b^{2}

   =-(9a^{2}-12ab+4b^{2})

   =-[(3a)^{2}-2.3a.2b+(2b)^{2}]

   =-(3a-2b)^{2}

   #DYNA

   Trả lời
2. a)

   0,125(a+2)^3-1

   = [0,5(a+2)]^3-1^3

   = (0,5a+1)^3-1^3

   = (0,5a+1-1)[(0,5a+1)^2+1.(0,5a+1)+1^2]

   = 0,5a(0,25a^2+a+1+0,5a+1+1)

   = 0,5a(0,25a^2+1,5a+3)

   b)

   -9a^2+12ab-4b^2

   = -(9a^2-12ab+4b^2)

   = -[(3a)^2-2.3a.2b+(2b)^2]

   = -(3a-2b)^2

   $#<33$

   Trả lời