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A=(2-1)(2+1)*...*(2^256+1)+1
=(2^2-1)(2^2+1)*...*(2^256+1)+1
=(2^4-1)(2^4+1)*...*(2^256+1)+1
=(2^8-1)(2^8+1)(2^16+1)(2^32+1)*....*(2^256+1)+1
=(2^16-1)(2^16+1)*....*(2^256+1)+1
=(2^32-1)(2^32+1)*...*(2^256+1)+1
=(2^64-1)(2^64+1)(2^128+1)(2^256+1)+1
=(2^128-1)(2^128+1)(2^256+1)+1
=(2^256-1)(2^256+1)+1
=2^512

a)\(A=\left(2+1\right)\left(2^2+1\right)...\left(2^{256}+1\right)+1.\)
\(< =>A=\left(2-1\right)\left(2+1\right)\left(2^2+1\right)...\left(2^{256}+1\right)+1\)
\(A=\left(2^2-1\right)\left(2^2+1\right)\left(2^4+1\right)....\left(2^{256}+1\right)+1\)
.....
\(=>A=\left(2^{256}-1\right)\left(2^{256}+1\right)+1\)\(=2^{512}-1+1=2^{512}\)
b) sai đề !
đề câu b phải là ( 5x - 3y +4z)(5x-3y-4z)=(3x-5y)^2 mới đúng

Bài 2:
a: \(\left(a-b-2\right)^2-\left(2a-2b\right)\left(a-b-2\right)+a^2-2ab+b^2\)
\(=\left(a-b\right)^2-4\left(a-b\right)+4+\left(a-b\right)^2-2\left(a-b\right)\left(a-b-2\right)\)
\(=2\left(a-b\right)^2-4\left(a-b\right)+4-2\left[\left(a-b\right)^2-2\left(a-b\right)\right]\)
\(=2\left(a-b\right)^2-4\left(a-b\right)+4-2\left(a-b\right)^2+4\left(a-b\right)\)
\(=4\)
b: \(\left(2+1\right)\left(2^2+1\right)\cdot...\cdot\left(2^{256}+1\right)-1\)
\(=\left(2^2-1\right)\left(2^2+1\right)\left(2^4+1\right)\cdot...\cdot\left(2^{256}+1\right)-1\)
\(=\left(2^4-1\right)\left(2^4+1\right)\left(2^8+1\right)\cdot...\cdot\left(2^{256}+1\right)-1\)
\(=\left(2^8-1\right)\left(2^8+1\right)\left(2^{16}+1\right)\cdot...\cdot\left(2^{256}+1\right)-1\)
\(=\left(2^{16}-1\right)\left(2^{16}+1\right)\left(2^{32}+1\right)\cdot...\cdot\left(2^{256}+1\right)-1\)
\(=\left(2^{32}-1\right)\left(2^{32}+1\right)\left(2^{64}+1\right)\cdot...\cdot\left(2^{256}+1\right)-1\)
\(=\left(2^{64}-1\right)\left(2^{64}+1\right)\left(2^{128}+1\right)\left(2^{256}+1\right)-1\)
\(=\left(2^{128}-1\right)\left(2^{128}+1\right)\left(2^{256}+1\right)-1\)
\(=\left(2^{256}-1\right)\left(2^{256}+1\right)+1\)
\(=2^{512}-1+1=2^{512}\)
c: \(24\left(5^2+1\right)\left(5^4+1\right)\cdot...\cdot\left(5^{32}+1\right)-5^{64}\)
\(=\left(5^4-1\right)\left(5^4+1\right)\left(5^8+1\right)\left(5^{16}+1\right)\left(5^{32}+1\right)-5^{64}\)
\(=\left(5^8-1\right)\left(5^8+1\right)\left(5^{16}+1\right)\left(5^{32}+1\right)-5^{64}\)
\(=\left(5^{16}-1\right)\left(5^{16}+1\right)\left(5^{32}+1\right)-5^{64}\)
\(=\left(5^{32}-1\right)\left(5^{32}+1\right)-5^{64}\)
=-1

Giúp vs @@Phạm Hoàng GiangTrần Quốc LộcTrần Thị Hươnghattori heijiTRẦN MINH HOÀNGAn Nguyễn BáRibi Nkok NgokKien Nguyen
Trần Đăng NhấtHung nguyen
Sửa đề bài 1 : Rút gọn
a,\(\left(2+1\right)\left(2^2+1\right)\left(2^4+1\right).........\left(2^{32}+1\right)-2^{64}\)

1/
Áp dụng phương pháp hệ số bất định ta có
x4-6x3+12x2-14x+3
= (x2+ax+b)(x2+cx+d)
= x4+ (a+c)x3+ (ac+b+d)x2+(ad+bc)x + bd
Đồng nhất đa thức trên với đề bài ta có hệ phương trình
\(\Rightarrow\left[{}\begin{matrix}a+c=-6\\ac+b+d=12\\ad+bc=-14\\bd=3\end{matrix}\right.\)
\(\Rightarrow\left[{}\begin{matrix}a=-2\\b=3\\c=-4\\d=1\end{matrix}\right.\)
Thay a,b,c,d vào ta được
x4-6x3+12x2-14x+3
= (x2+ax+b)(x2+cx+d)
= (x2-2x+3)(x2-4x+1)


đặt A = (2 + 1)(22 + 1)...(2256 + 1).
khi đó (2 - 1)A = (2 -1)(2 + 1)(22 + 1)...(2256 + 1)
suy ra A = 2257 - 1 (dùng hiệu hai bình phương).
nên biểu thức đã cho là A + 1 = 2257.
\(A=3\left(2^2+1\right)\left(2^4+1\right)...\left(2^{256}+1\right)+1\)
\(A=\left(2^2-1\right)\left(2^2+1\right)\left(2^4+1\right)...\left(2^{256}+1\right)+1\) ( do \(3=2^2-1\) nhé bạn)
\(A=\left(2^4-1\right)\left(2^4+1\right)...\left(2^{256}+1\right)+1\) ( do \((2^2-1)(2^2+1)=2^4-1\) Đây là hằng đẳng thức \(a^2-b^2=(a-b)(a+b)\)
\(A=\left(2^8-1\right)\left(2^8+1\right)...\left(2^{256}+1\right)+1\)
....
\(A=\left(2^{256}-1\right)\left(2^{256}+1\right)+1\)
\(A=2^{512}-1+1=2^{512}\)
Vậy \(A=2^{512}\)