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mình xin nhầm đề là: A = \(1*2*3+2*4*6+4*8*12+8*16*24 \over2*3*4+4*6*8+8*12*16+16*24*32\)
a, \(\frac{1}{2}+\frac{1}{6}+\frac{1}{12}+\frac{1}{20}+\frac{1}{30}+\frac{1}{42}=\frac{1}{1.2}+\frac{1}{2.3}+\frac{1}{3.4}+\frac{1}{4.5}+\frac{1}{5.6}+\frac{1}{6.7}\)
= \(\frac{1}{1}-\frac{1}{2}+\frac{1}{2}-\frac{1}{3}+\frac{1}{3}-\frac{1}{4}+\frac{1}{4}-\frac{1}{5}+\frac{1}{5}-\frac{1}{6}+\frac{1}{6}-\frac{1}{7}\)
= \(1-\frac{1}{7}=\frac{6}{7}\)
\(A=\frac{1}{2}+\frac{1}{4}+\frac{1}{8}+\frac{1}{16}+\frac{1}{32}+\frac{1}{64}\)
\(A=\frac{32+16+8+4+2+1}{64}\)
\(A=\frac{63}{64}\)
Chúc bạn học tốt và tíck cho mìk vs nha!
cach 1
A=1/2+1/4+1/8+1/16+1/32+1/64
ta thấy:1/2=1-1/2; 1/4 = 1/2 - 1/4;... ;1/64 = 1/32 - 1/64
A = 1-1/2+1/2-1/4+1/4-1/8+1/8-1/16+1/16-1/32+1/32-1/64
A=1-1/64
A=63/64
cách 2
A=1/2+1/4+1/8+1/16+1/32+1/64
A x 2=1+1/2+1/4+1/8+1/16+1/32
A x 2 - A= (1+1/2+1/4+1/8+1/16+1/32)-(1/2+1/4+1/8+1/16+1/32+1/64)
A x 2 = 1-1/64
A x 2 =63/64
A =63/64 : 2
A = 63/128
2A = 1 + 1/2 + 1/4 + 1/8 + 1/16 + 1/32
2A - A = (1 + 1/2 + 1/4 + 1/8 + 1/16 + 1/32) - (1/2 + 1/4 + 1/8 + 1/16 + 1/32 + 1/64)
A = 1 - 1/64
A = 63/64
\(A=\frac{1}{2}+\frac{1}{4}+\frac{1}{8}+\frac{1}{16}+\frac{1}{32}+\frac{1}{64}\)
\(2A=1+\frac{1}{2}+\frac{1}{4}+\frac{1}{8}+\frac{1}{16}+\frac{1}{32}\)
\(2A-A=\left(1+\frac{1}{2}+\frac{1}{4}+\frac{1}{8}+\frac{1}{16}+\frac{1}{32}\right)-\left(\frac{1}{2}+\frac{1}{4}+\frac{1}{8}+\frac{1}{16}+\frac{1}{32}+\frac{1}{64}\right)\)
\(A=1-\frac{1}{64}=\frac{63}{64}\)
8 x 12 x 32 + 4 x 27 x 24 + 41 x 6 x 16
=96 x 32 + 96 x 27 + 96 x 41
=96 x (32 + 27 + 41)
= 96 x 100
=9600
A = 8 × 12 × 32 + 4 × 27 × 24 + 41 × 6 × 16
A = 8 × 12 × 32 + 4 × 24 × 27 + 6 × 16 × 41
A = 96 × 32 + 96 × 27 + 96 × 41
A = 96 × (32 + 27 + 41)
A = 96 × 100
A = 9600
= 32+0+32x8+32= 32x(1+8+1)=32x10=320