\(\left(45\cdot46+47\cdot48\right)\cdot\left(51\cdot52-49\cdot48\right)\cdot\left(45\cdot128-90\cdot64\right)\cdot\left(1995\cdot1996+1997\cdot1998\right)\)

\(=\left(45\cdot46+47\cdot48\right)\cdot\left(51\cdot52-49\cdot48\right)\cdot\left(45\cdot2\cdot64-90\cdot64\right)\cdot\left(1995\cdot1996+1997\cdot1998\right)\)

\(=\left(45\cdot46+47\cdot48\right)\cdot\left(51\cdot52-49\cdot48\right)\cdot\left(90\cdot64-90\cdot64\right)\cdot\left(1995\cdot1996+1997\cdot1998\right)\)

\(=\left(45\cdot46+47\cdot48\right)\cdot\left(51\cdot52-49\cdot48\right)\cdot0\cdot\left(1995\cdot1996+1997\cdot1998\right)\)

\(=0\)

 (45 x 46 + 47 x 48) x (51 x 52 - 49 x 48) x (45 x 128 - 90 x 64) x (1995 x 1996 + 1997 x 1998)

=            A              x             B             x (45 x 128 - 45 x 2 x 64) x                C

= A x B x (45 x 128 - 45 x 128) x C

=A x B x 0 x C

=0

kết quả bằng 0

b) (45 x 46 + 47 x 48) x (45 x 128 - 90 x 64) x (2009 x 2010 + 2011 x 2012)

= (45 x 46 + 47 x 48) x (45 x 2 x 64 - 45 x 2 x 64) x (2009 x 2010 + 2011 x 2012)

= (45 x 46 + 47 x 48) x 0 x (2009 x 2010 + 2011 x 2012) = 0

( 51 x 52 - 49 x 48 ) x ( 45 x 128 ) x ( 45 x128 - 90 x 64) x ( 1995 x 1996 x 1997)

= ( 51 x 52 - 49 x 48 ) x ( 45 x 128 ) x ( 5760 - 5760 ) x ( 1995 x 1996 x 1997)

= ( 51 x 52 - 49 x 48 ) x ( 45 x 128 ) x 0 x ( 1995 x 1996 x 1997)

= 0.

#Y/n

* là gì z bn

Dấu nhân bạn ạ!

Ta nhận thấy :

45 x 128 – 90 x 64 = 45 x (2 x 64) – 90 x 64

          = (45 x 2) x 64 – 90 x 64

          = 90 x 64 – 90 = 0

Trong 1 tích có 1 thừa số bằng 0. Vậy tích đó bằng 0, tức là :

(45 x 46 + 47 x 48) x (51 x 52 – 49 x 48) x (45 x 128 – 90 x 64) x (1995 x 1996 + 1997 x 1998) = 0

c, Ta nhận thấy:
45 x 128 – 90 x 64 = 45 x (2 x 64) – 90 x 64
= (45 x 2) x 64 – 90 x 64
= 90 x 64 – 90 = 0
Trong 1 tích có 1 thừa số bằng 0. Vậy tích đó bằng 0, tức là:

(45 x 46 + 47 x 48) x (51 x 52 – 49 x 48) x (45 x 128 – 90 x 64) x (1995 x 1996 + 1997 x 1998) = 0

\(a,\left(x-15\right)\times7-270=169\times45\\ \left(x-15\right)\times7-270=7605\\ \left(x-15\right)\times7=7605+270\\ \left(x-15\right)\times7=7875\\ x-15=7875:7\\ x-15=1125\\ x=1125+15\\ x=1140\\ b,64-\left(34\times x-8\right)=4\\ 34\times x-8=64-4\\ 34\times x-8=60\\ 34\times x=60+8\\ 34\times x=68\\ x=68:34\\ x=2\)