Đặt A = 20 + 21 + 22 + 23 + ... + 250
2A = 21 + 22 + 23 + 24 + ... + 251
2A - A = (21 + 22 + 23 + 24 + ... + 251) - (20 + 21 + 22 + 23 + ... + 250)
A = 251 - 20
A = 251 - 1 < 251
Vậy 20 + 21 + 22 + 23 + ... + 250 < 251
Ủng hộ mk nha ^_-
Bai 1 : Tu nam so 1;3;9;27;81 co the lap dc bao nhieu ti le thuc ?
Bai 2: Mot manh dat hcn dien tich 153m2 co chieu rong bang 4/17 chieu dai . Tinh chieu rong , chieu dai cua manh dat
Bai 3: Ti so cua hai so bang 3:4 .Neu them 1,5 vao so thu nhat thi ti o cua chung se bang 6:7 . Tim 2 so do
bai 1: Cho cac don thuc A=-4/9x^3y va B= 3/8 x^5y^3. Tim cac cap gia tri (x;y)de A,B cung gia tri am
bai 2: viet don thuc B=64xy^12 duoi dang luy thua cua 1 don thuc voi so mu khac 1
bai 3: cho A=8x^5y^3; B=-3x^6y^3; C=-6x^7y^2. CM: Ax^2+Bx+C>0
bai 1 tim cac stn x y z sao cho x+y+z=xyz
bai 2cmr neu m^2+mn+n^2chia het cho 9 voi m ,n la cac stn thi m,n chia het cho 3
bai 3 tim stn n nho nhat de cac phan so sau toi gian
7/n+9.8/n+10,...,31/n+33
bai 4chung to rang phan so m^3+2m/m^4+3m^2 +1 toi gian
bai 5 a,cmr khong ton tai so chinh phuong nao co dang abab
b,cho 51 so nguyen duong khong vuot qua 100 cmr ton tai 2 so trong 51 so noi tren ma 1 so chia het cho so con lai
c,tim cac so co 3 chu so sao cho hieu cua so ay va gom 3 chu so ay viet theo thu tu nguoc lai la mot so chinh phuong
bai 6cmr A=2x(x+y-1)+y^2+1 luon nhan gia tri khong am voi moi x,y
bai 7 tim hai so nguyen duong sao cho tong ,hieu thuong (so lon chia cho so nho )cua chung cong lai duoc 38
bai 8 cho ba so a,b,c thoa man a/2009=b/2010=c/2011
tinh gia tri cua bieu thuc M=4(a-b)(b-c)-(c-a)^2
giup wm giai bai toan nay
cho: -1\2=y-2\3=z-3\4 va 2x+y-z=50
tim x,y,z
bai 4 so sanh cac so thuc
\(\frac{4}{9}va\)0,4(5)
\(\sqrt[2]{3}va\sqrt[3]{2}\)
Hihihi.Hi moi nguoi.Minh se dat mot cau hoi ve dai so lop 7,mong moi nguoi chi giai><,boi vi toan minh hoc chua gioi lam nen co cac bai toan con thac mac,len day de mong nhan duoc su giup do,de toan nhu sau:(1)Da thuc P(x)=x2016 +2013x + 2012 co ngiem duong khong?Vi sao?. 2 Bai nua nhe(*^-^*):
(2)Cho hai da thuc: M(x)=2,52 -0,5x-x3-1
1/2N(x)=-x3+2,5x2-6+2x
a)Tim A(x)=M(x)-N(x).Sau do tim mot ngiem cua da thuc A(x)
b)Tim da thucB(x) biet B(x)=M(x)+N(x).Cho biet bac cua da thuc B(x).
(3)Cho da thuc:f(x)=ab2 + bx + c.Chung to neu f(x) co ngiem x=-1 thi b=a+c.
MOT BAI NUA THOI MA.NHA NHA NHA MOI NGUOI^_^:
(4)Cho hai da thuc:A=(-1/2axy3)2 va B=(-3a2 x2)3 (a la hang so khac 0).
a)Tinh M=A.B roi cho biet he so va phan bien cua M
b)Tim bac cua M.
AI CO CAU TRA LOI NHAN TIN TRA LOI CHO MINH BIET NHAAAAA.CAM ON!!!!!.
Bạn Nam da co 1 so bai kiem tra mon toan .Nam thay neu them 3 diem 10 va mot diem 9 thi diem trung binh cua minh la 8 .Neu chi duoc them 2 diem 10 va mot diem 9 thi diem trung binh bang 7,5 .Hoi diem trung binh cua Nam hien nay la bai nhieu
Cho minh hoi bai nay. Chi can tra loi 1 cau cung duoc! Tick cho ai tra loi som nhat, day du nhat.
1. Cho so huu ti y=2a-1/-3. Voi gia tri nao cua a thi y la so duong, y la so am, khong phai so duong cung phai so am?
2. Cho so huu ti x=a-5/a (a khac 0). Voi gia tri nao cua a thi x la so nguyen?
3. Cho so huu ti x=a-3/2a (a khac 0). Voi gia tri nao cua a thi x la so nguyen?
8-1 X 0 +2 :2
AI GIAI DC BAI NAY CHO LAM SU PHU
