Bài 2 : 1 + ( -2 ) + 3 + ( -4 ) + ... + 2015
= [ 1 + ( -2 ) ] + [ 3 + ( -4 ) ] + ... + 2015
= -1 + -1 + ... + 2015
Có số các cặp số bằng ( -1 ) là :
2014 : 2 = 1007 ( cặp )
= -1007 + 2015
= 1008
bai 1: thuc hien phep tinh a) 62 : 4 . 3 + 2 . 52
b) 5 . 42 - 18 : 32
c) 2448 : [ 119 - ( 23 - 6 )
bai 2 : tim x , biet :
a) 125 - 5 ( x + 4 ) = 38
b) (3x - 24) . 73 - 2 . 74
c) 70 : x , 84 : x va x > 8
d) x : 12, x : 25 , x : 30 va 0 < x < 500
bai 3 : So hoc sinh khoi 6 cua mot truong khoang tu 200 den 400 khi xep hang 12 hang,15 hang 18 hang vua du . Tinh so hoc sinh do
bai 1: Tinh nhanh
a) 1/2 + 1/4 + 1/8 + 1/16 + 1/32
b) 1/2 x 1/2 + 1/2 x 1/3 + 1/3 + 1/3 + 1/4 + 1/4 x 1/5 + 1/5 x 1/6
Bai 1: Tinh
A = 253 x 75 - 161 x 37 + 253 x 25 - 161 x 63 / 100 x 47 - 12 x 3,5 - 5,8 : 0,1
Bai 2: Tim quy luat va tinh tong cua moi day:
a,1;3;9;27;...;729
b,1;2;4;8;...;2048
c,1;4;9;16;...;1089
Minh se tich diem cho cac ban ! giai ra nhe cac ban!
Bai 1 : Tim x , biet :
a) (32 - x ) + (-7 +I x I ) - (I x I + 25 ) = 25
32-x-7+I x I - 25 = 25 ( bước này cô mk làm hộ )
b) 1 + { -2 - [ -3 +( -4 + I x I)]} = 1-[2-(-3-4)]
Tinh gia tri bieu thuc
a, A = x^2 + x - 5 voi x = -3
b, B = | x -1 | + | x +9| voi x = -81
c, C = -7x^3 × | x -1| + 42 voi x = -1
d, D= -(x -1) × (x+2) voi |x| = 2
Bai 1 : Tinh a) 24 - (-15) - 2 b) (-85) + 10 - (-85) - 50 c) 71 - (-30) - (+18) + (-30)
d) -(30) - (+37) + (+37) + (-85) e) (35-815) - (795-65) g) (2002-79+15) + (-79+15)
h) -(515-80+91) - (2003+80-91)
Bai 2: Tim x,biet a) 25 - (30+x) = x - (27-8) b) (x-12) - 15 = (20-17) - (18+x) c) 15 - x = 7 - (-2) d) x - 35 = (-12) - 3 e) I5-xI - 26 = - 15
bai 1
cho bieu thuc A = 5/n+1 voi N THUOC Z
a, de A la phan so thi n co dieu kien gi ?
b , tim tat ca cac gia tri nguyen cua n de gia tri A la 1 so nguyen ?
bai 2
cho bieu thuc M = 6/n-3 voi n thuoc Z .Co bao nhieu gia tri cua n de :
a, M ko phai la phan so
b , M la phan so va cp gia tri nguyen ?
bai 3 viet tap hop cacs so nguyen sao cho :
-12/4 < x <6/3
Bai 1: Tim x
a)\(4^5+4^5+4^5+4^5.6^5+6^5+6^5+6^5+6^5+6^5=2^x\)
b)\(x\left(x+3\right)^{100}\)\(=\left(x+3\right)^{100}\)
-5/8=x/16
Y/10=(-4)/8
Bai 8:
1) x/3-1/4=(-5)/6
2) x+3/15=1/3
3) x-12/4=1/2
4) 3/4x=1/2