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a: \(=1995^2-\left(1995^2-1\right)=1995^2-1995^2+1=1\)
b: \(=18^8-18^8+1=1\)
c: \(=\left(163+37\right)^2=200^2=40000\)
a)
\(x^4+1996x^2+1995x+1996\)
\(=\left(x^4-x\right)+\left(1996x^2+1996x+1996\right)\)
\(=x\left(x^3-1\right)+1996\left(x^2+x+1\right)\)
\(=x\left(x-1\right)\left(x^2+x+1\right)+1996\left(x^2+x+1\right)\)
\(=\left(x^2+x+1\right)\left[x\left(x-1\right)+1996\right]\)
\(=\left(x^2+x+1\right)\left(x^2-x+1996\right)\)
b)
\(x^4+1997x^2+1996x+1997\)
\(=\left(x^4-x\right)+\left(1997x^2+1997x+1997\right)\)
\(=x\left(x^3-1\right)+1997\left(x^2+x+1\right)\)
\(=x\left(x-1\right)\left(x^2+x+1\right)+1997\left(x^2+x+1\right)\)
\(=\left(x^2+x+1\right)\left[x\left(x-1\right)+1997\right]\)
\(=\left(x^2+x+1\right)\left(x^2-x+1997\right)\)
x4+1996x2+1995x+1996
=(x4_x)+(1996x2+1996x+1996)
=x(x3-1)+1996(x2+x+1)
=x(x-1)(x2+x+1)+1996(x2+x+1)
=(x2+x+1)((x2-1)+1996)
=(x2+x+1)((x+1)(x-1)+1996)
Câu 2 tương tự bạn nhé!
1) A=19952-1994.1996
=19952-(1995-1)(1995+1)
=19952-(19952-1)
=1
2) B=98.28-(184-1)(184+1)
=(9.2)8-[(184)2-1]
= 188-188+1
=1
3) C=1632+74.163+372
=1632+2.37.163+372
=1632+2.163.37+372
=(163+37)2.2
=80000
\(M=1995^2-1994.1996\)
\(=1995^2-\left(1995-1\right)\left(1995+1\right)\)
\(=1995^2-\left(1995^2-1\right)=1\)
\(N=9^8.2^8-\left(18^4-1\right)\left(18^4+1\right)\)
\(=18^8-\left(18^8-1\right)=1\)
\(K=99^3+3.99^2+3.99+1\)
\(=99^3+3.99^2.1+3.99.1^2+1^3\)
\(=\left(99+1\right)^3\)
\(=100^3=1000000\)
Chúc bạn học tốt.
Bài làm:
c) \(M=1995^2-1994.1996=1995^2-\left(1995-1\right)\left(19995+1\right)=1995^2-1995^2+1^2=1\)
d) \(N=9^8.2^8-\left(18^4-1\right)\left(18^4+1\right)=18^8-18^8+1^2=1\)
e) \(K=99^3+3.99^2+3.99+1=\left(99+1\right)^3=100^3=1000000\)
Học tốt!!!!!
Ta có: A = 6 + 52 + 53 + 54 + ... + 51996 + 51997
A = 1 + 5 + 52 + 53 + ... + 51996 + 51997
5A = 5(1 + 5 + 52 + 53 + ... + 51996 + 51997)
5A = 5 + 52 + 53 + 54 + ... + 51997 + 51998
5A - A = (5 + 52 + 53 + 54 + ... + 51997 + 51998) - (1 + 5 + 52 + 53 + ... + 51996 + 51997)
4A = 51998 - 1
A = \(\frac{5^{1998}-1}{4}\)
A= 6 + 52+ 53+ 54 + ..... + 5 1996+ 51997
=>5A=5+52+53+54+...+51997+51998
=5A-A=(5+52+53+54+...51997+51998)-(1+5+52+53+...+51996+51997)
=4A=51998-1=>A=\(\frac{5^{1998}-1}{4}\)
Vậy ...
hc tốt
Vì xy + yz + xz = 0 nên 2 (xy + yz + xz) = 0
Vì x + y + z = 0 nên (x+y+z)^2 =0
suy ra x^2 + y^2 + z^2 + 2 (xy+yz+xz) = 0
suy ra x^2 + y^2 + z^2 = 0
suy ra x = y = z = 0
Thay vào S, ta được:
S = (0-1)^1995 + 0^1996 + (z+1)^1997 = (-1) + 0 + 1 = 0
Vậy S = 0
Vì xy + yz + xz = 0 nên 2 (xy + yz + xz) = 0
Vì x + y + z = 0 nên (x+y+z)^2 =0
suy ra x^2 + y^2 + z^2 + 2 (xy+yz+xz) = 0
suy ra x^2 + y^2 + z^2 = 0
suy ra x = y = z = 0
Thay vào S, ta được:
S = (0-1)^1995 + 0^1996 + (z+1)^1997 = (-1) + 0 + 1 = 0
Vậy S = 0
\(F=\frac{1996^3-1}{1996^2+1997}=\frac{\left(1996-1\right)\left(1996^2+1996+1\right)}{1996^2+1997}=\frac{1995.\left(1996^2+1997\right)}{1996^2+1997}=1995\)
E = \(\frac{1995^3}{1995^2-1994}=\frac{1995^3+1-1}{1995^2-1994}=\frac{\left(1995+1\right)\left(1995^2-1995+1\right)-1}{1995^2-1994}\)
=\(\frac{1996\left(1995^2-1994\right)-1}{1995^2-1994}=1996-\frac{1}{1995^2-1994}\)
Vì \(1995^2-1994>0\) => \(\frac{1}{1995^2-1994}<1\) => \(-\frac{1}{1995^2-1994}>-1\) => \(1996-\frac{1}{1995^2-1994}>1996-1\)
HAy E > F
1001\(^2\)=(1000+1)\(^2\)=1000\(^2\)-2.1000+1
=1000000-2000+1
=tự tính
bài a đơn giản lắm:
99.101 = (100 - 1)(100 + 1)
= 1002 - 1 ( 12 thì tất nhiên = 1 rồi)
= 9999 ( số đẹp ghê!)
c) 19952 - 1994.1996 = 19952 - (1995 - 1) (1995 + 1)
= 19952 - (19952 - 1)
= 19952 - 19952 + 1
= 1