1) Tim A , biet :
(242 / 363 - 1616 / 2121) = 2 / 7 x A
2)Thuc hien phep tinh :
99 / 98 - 98 / 97 + 1 / 97 x 98
thuc hien phep tinh
a) S1=2+2^2+2^3+...+2^90
b)S2= (-2) +(-2)^2 +(-2)^3+...(-2)^100
c)S3=2^100-2^99-2^98-2^97-...-2^2-2-1
d)S4=1-3+5-7+...+2001-2003+2005-
\(x = {-b \pm \sqrt{b^2-4ac} \over 2a}\)
khong thuc hien phep tinh , hay so sanh : 99 x 99 va 98 x 100
Ta có: 99x99=99x(98+1) = 99x98+99
98x100= 98x(99+1) = 98x99+98
Ta có: 98x99=98x99 mà 99> 98 => 99x99>98x100
tim a biet :
242/363 + 1616/2121 = 2/7*a
242/363 + 1616/2121 = 2/7 x a
10/7 = 2/7 x a
a = 10/7 : 2/7
a = 5
Sao bài lớp cậu giống bài lớp tớ thế? Lớp mấy v
tinh : 1+2-3+4+5+6+7+8+9+...+97+98-99
tim x: 1-|x+1|=-7
tinh gia tri bieu thuc : a ) : (1+2+3+4+ .............+97+98+99+100) : 5
Tổng các số trong trong ngoặc là:(100+1).[(100-1):1+1]:2=5050
a=5050:5=1010
1) Thuc hien phep tinh (nhanh neu co the):
a) 21.(-35)-3.(-25).7
b) 77-11.(30+7)
c) 85.(35-27)-35.(85-27)
d) (-25).68+(-34).(-250)
e) 125.(-61).(-23).(-1)2n+1/ n thuoc N
f) 1-2+3-4+...+49-50+51
g)1-2-3+4+5-6-7+...+97-98-99+100
h) 2100-299-298-...-22-2-1
Làm đc câu nào thì làm nha
a) 21.(-35)-3.(-25).7=21.(-35)-(21.(-25)=21(-35+25)=21.(-10)=-210
b)77-11(30+7)=77-11.7+11.30=77-77-330=-330
c)85(35-27)-35(85-27)=85.35-85.27-35.85+35.27=(85.35-35.85)+(35.27-85.27)=35.27-85.27=27(35-85)=27.(-50)=-1350
d)(-25).68+(-34).(-250)=-25.68+34.2.125=-25.68+68.125=68(125-25)=68.100=6800
e)125.(-61).(-2^3).(-1)^2n+1=125.(-61).(-8).(-1)=(-8.125).61=-1000.61=-61000
h) đặt S=2100-299-298-...-22-2-1=2^100-(2^99+2^98+2^97+...+2+1)=2^100-A
ta có: A=2^99+2^98+2^97+...+2+1
2A=2^100+2^99+2^98+...+2^2+2
=>2A-A=(2^100+2^99+2^98+...+2^2+2)-(2^99+2^98+2^98+...+2+1)
=>A=2^100-1
=>S=2^100-(2^100-1)=2^100-2^100+1=1
A=2^100
a là bằng -210
ý b bằng -330
ý c bằng -1350
ý d bằng 6800
ý f bằng 225
tớ làm được 5 ý , tich nha bạn
a, 21.(-35)-3.(-25).7
=21.(-35)-(3.7).(-25)
=21.(-35)-21.(-25)
=21.[(-35)-(-25)]
=21.(-10)
=-210
THUC HIEN PHEP TINH
1+1^3+1^4+... +1^98 +1^99
help me mik like
1 + 13 + 14 + ............. + 198 + 199 (98 số hạng)
= 1 + 1 + 1 + 1 + .......... + 1 (98 số hạng)
= 98 . 1
= 98
tinh tong gia tri bieu thuc :
a)A=1+1/3+1/5+...+1/97+1/99/1/1*99+1/3*97+1/5*95+...+1/97*3+1/99*1
b)B=1/2+1/3+1/4+...+1/100/99/1+98/2+97/3+...+1/99
Tính \(T=\left(\frac{2}{98}+\frac{3}{97}+...+\frac{99}{1}\right)X\left(\frac{1}{99}+\frac{2}{98}+...+\frac{98}{2}\right)-\left(\frac{1}{99}+\frac{2}{98}+..+\frac{99}{1}\right)X\left(\frac{2}{98}+\frac{3}{97}+...+\frac{98}{2}\right)\)