tính nhanh các kết quả sau
a)1995^2-1994.1996
b)9^8.2^8-(18^4-1)(18^4+1)
c)163^2+74.163+37^2
d)\(\frac{1993^2-1}{1996^2+1997}\)
Tính Nhanh
A= 1995^2 -1994.1996
B= 9^8.2^8-(18^4-1).(18^4+1)
C=163^2+74.163+37^2
D=127^2+146.127+73^2
MẤY BẠN GIÚP MÌNH VỚI MÌNH CẦN GẤP LẮM
A = 19952 - ( 1995-1) (1995+1)
= 19952 - (19952 - 12)
= 19952 - 19952 +1
= 1
Bài 7. Tính nhanh
a/ 498mũ 2
b/ 93. 107
c/ 163 mũ 2+ 74.163 + 37mũ 2
d/ 1995 mũ 2 – 1994.1996
e/ 9 mũ 8.2 mũ 8 – (18mũ 4 – 1)(18 mũ 4+ 1)
f/ 125 mũ 2 - 2. 125. 25 + 25 mũ 2
Bài 8. Rút gọn các biểu thức sau
a/ (x mũ 2+ 3x+ 1)mũ 2 + (3x – 1) mữ 2 – 2(x mũ 2+ 3x+ 1)(3x– 1)
b/ (3x mũ 3+ 3x + 1)(3x mũ 3– 3x +1) – (3xmũ 3+1)mũ 2
c/ (2xmũ2+ 2x + 1)(2xmũ2 – 2x + 1) – (2xmũ 2+ 1)mũ 2
Bài 9. Rút gọn rồi tính giá trị biểu thức
a/ A = (2x + y)mũ 2 - (2x + y) (2x - y)+ y(x - y) vì x= - 2; y= 3.
b/ B = (a - 3b)mũ 2 - (a + 3b)mũ 2 - (a -1)(b -2 ) vì a =1/2; b = -3.
MN GIÚP MIK VS MIK CẦN GẤP
Bài 9:
a) Ta có: \(A=\left(2x+y\right)^2-\left(2x+y\right)\left(2x-y\right)+y\left(x-y\right)\)
\(=4x^2+4xy+y^2-4x^2+y^2-xy-y^2\)
\(=3xy-y^2\)
\(=3\cdot\left(-2\right)\cdot3-3^2=-18-9=-27\)
b) Ta có: \(B=\left(a-3b\right)^2-\left(a+3b\right)^2-\left(a-1\right)\left(b-2\right)\)
\(=a^2-6ab+9b^2-a^2-6ab-9b^2-ab+2a+b-2\)
\(=-13ab+2a+b-2\)
\(=-13\cdot\dfrac{1}{2}\cdot\left(-3\right)+2\cdot\dfrac{1}{2}+\left(-3\right)-2\)
\(=\dfrac{31}{2}\)
Bài 7:
a) \(498^2=\left(500-2\right)^2=250000-2000+4=248004\)
b) \(93\cdot107=100^2-7^2=10000-49=9951\)
c) \(163^2+74\cdot163+37^2=\left(163+37\right)^2=200^2=40000\)
d) \(1995^2-1994\cdot1996=1995^2-1995^2+1=1\)
e) \(9^8\cdot2^8-\left(18^4-1\right)\left(18^4+1\right)\)
\(=18^8-18^8+1=1\)
f) \(125^2-2\cdot125\cdot25+25^2=\left(125-25\right)^2=100^2=10000\)
Bài 8:
a) Ta có: \(\left(x^2+3x+1\right)^2-2\left(x^2+3x+1\right)\left(3x-1\right)+\left(3x-1\right)^2\)
\(=\left(x^2+3x+1-3x+1\right)^2\)
\(=\left(x^2+2\right)^2\)
\(=x^4+4x^2+4\)
b) Ta có: \(\left(3x^3+3x+1\right)\left(3x^3-3x+1\right)-\left(3x^3+1\right)^2\)
\(=\left(3x^3+1\right)^2-9x^2-\left(3x^3+1\right)^2\)
\(=-9x^2\)
c) Ta có: \(\left(2x^2+2x+1\right)\left(2x^2-2x+1\right)-\left(2x^2+1\right)^2\)
\(=\left(2x^2+1\right)^2-4x^2-\left(2x^2+1\right)^2\)
\(=-4x^2\)
tính nhanh:
1) A=19952 - 1994.1996
2) B=98.28-(184-1).(184+1)
3) C= 1632+74.163+372
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
Tính nhanh: M=1-2-3+4+5-6-7+8+...+1993-1994-1995+1996+1997
(1-2-3+4)+(5-6-7+8)+.....+(1993-1994-1995+1996)+1997
=0+0+....+0+1997
=1997
Tính nhanh:
M=1-2-3+4+5-6-7+8+...+1993-1994-1995+1996+1997
Tính nhanh:
a/ 1995^2 - 1994 . 1996
b/ 9^8 . 2^8 - (18^4 - 1) ( 18^4 + 1)
Tinh nhanh: M=1-2-3+4+5-6-7+8+...+1993-1994-1995+1996+1997
Tính hợp lí:
a) A= 1995^3+1/1995^2-1994
b) B= 3^8.7^8-(21^4-1).(21^4+1)
c) C= 163^2+74.163+37^2
d) E= 147^2-94.147+47^2
e) F= 3^24-(27^4+1).(9^6-1)
f) D= (2^2+4^2+...+100^2)-(1^2-3^2+...+99^2)
Tinh nhanh:
1-2-3+4+5-6-7+8+.........1993-1994-1995+1996+1997