tinh gia tri bieu thuc: B=1*2*3+2*3*4+3*4*5+...+17*18*19
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tinh gia tri cua bieu thuc: B=1*2*3+2*3*4+3*4*5+4*5*6+.....+17*18*19
tinh gia tri cua bieu thuc B={1(1/5).[4.(3+1/3-3/7-3/53)]/[3+1/3-3/7-3/53]}:{[4+4/17+4/19+4/2003]/5+5/17+519+5/2003]}
tinh gia tri bieu thuc 1+2+3...+16+17+18
cho bieu thuc a=-1/3+1/3^2-1/3^3+1/3^4-1/3^5+...+1/3^100 tinh gia tri cua bieu thuc b=4/a/+1/3^100
giup to hai bai nay
1. gia tri X thoa man 4x*(5x-1)+10x*(2-2x)=16
gia tri x thoa man (x^2+1)*(x^2+5)
2. tinh gia tri bieu thuc A
A=(202+182+162+...+42+22)-(192+172+152+...+32+12)
a) Tinh gia tri bieu thuc:
3/5 : 4/5 + 1/2 x 2/3
b) Tim x:
5/4 nhan x = 3/8 + 1/4
A
\(\frac{3}{5}\div\frac{4}{5}+\frac{1}{2}\times\frac{2}{3}\)
\(=\frac{3}{4}+\frac{1}{3}\)
\(=\frac{13}{12}\)
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B
\(\frac{5}{4}\times x=\frac{3}{8}+\frac{1}{4}\)
\(\frac{5}{4}\times x =\frac{5}{8}\)
\(x=\frac{5}{8}\div\frac{5}{4}\)
\(x=\frac{4}{8}=\frac{1}{2}\)
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tinh gia tri bieu thuc B= 1+2-3-4+5+6-...-303-304+305+306
Cho phan thuc B=(3\y+3)+(1\y-3)-(18\9-y2)
a)Tim dieu kien cua y de gia tri cua bieu thuc B duoc xac dinh
b)Rut gon bieu thuc B
c)Tinh gia tri cua B de B co gia tri nguyen
cho x+y =1 . tinh gia tri cua bieu thuc A=x^3+y^3+3xy
chox-y=1. tinh gia tri cua bieu thuc B=x^3-y^3-3xy
cho x+y=1 . tinh gia tri cua bieu thuc C=x^3+y^3+3xy(x^2+y^2)+6x^2*y^2(x+y)
Câu 1: Ta có: A = \(x^3+y^3+3xy=x^3+y^3+3xy\times1=x^3+y^3+3xy\left(x+y\right)\)
\(=\left(x+y\right)^3=1^3=1\)
Câu 2: Ta có: \(B=x^3-y^3-3xy=\left(x-y\right)\left(x^2+xy+y^2\right)-3xy\)
\(=x^2+xy+y^2-3xy=x^2-2xy+y^2=\left(x-y\right)^2=1^2=1\)
Câu 3: Ta có: \(C=x^3+y^3+3xy\left(x^2+y^2\right)-6x^2.y^2\left(x+y\right)\)
\(=x^3+y^3+3xy\left(x^2+2xy+y^2-2xy\right)+6x^2y^2\)
\(=x^3+y^3+3xy\left(x+y\right)^2-3xy.2xy+6x^2y^2\)
\(=x^3+y^3+3xy.1-6x^2y^2+6x^2y^3\)
\(=x^3+y^3+3xy\left(x+y\right)=\left(x+y\right)^3=1^3=1\)
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