\(\left(a+b-c\right)^2-\left(a-c\right)^2-2ab+2bc\)
\(=\left(a-c\right)^2+2b\left(a-c\right)+b^2-\left(a-c\right)^2-2ab+2bc\)
\(=2b\left(a-c\right)+b^2-2ab+2bc\)
\(=2ab-2bc+b^2-2ab+2bc=b^2\)
rut gon bieu thuc :
a,\(\left(a+b\right)^3-\left(a-b\right)^3-6a^2b\)
b,\(\left(a+b\right)^3+\left(a-b\right)^3-6ab^2\)
rut gon bieu thuc :
\(\left(x+1\right)^4-6\left(x+1\right)^2-\left(x^2-2\right).\left(x^2+2\right)\)
1) Rut gon cac bieu thuc sau :
a) (x-3)(x2+3x+ 9)-(54+x3)
b) (3x+y)(9x2-3xy +y2)-(3x-y)(9x2+3xy+y2)
2, Dien cac don thuc thich hop vao cho trong
a, (x+3y) (... - ... + ...) = x^3 +27y^3
b, (2x- ....) (... + 6xy + ... +...) = 8x^3 - 27y^3
Rút gọn biểu thức:
c, (a+b-c)^2-(a-c)^2-2ab+2bc
d, (a+b+c)^2+(b+c-a)^2+(c+a-b)^2+(a+b-c)^2
1) Rut gon cac bieu thuc sau :
a) (x-3)(x2+3x+ 9)-(54+x3)
b) (3x+y)(9x2-3xy +y2)-(3x-y)(9x2+3xy+y2)
2) Chung minh rang:
a) a3+b3= (a+b)3 -3ab(a+b)
b) a3-b3=(a-b)3 +3ab(a-b)
Ap dung : Tinh a3+b3 biet ab=12va a+b =-7
nhah nha mk dang can rat gap
rut gon
a)(2x+1)^2+2(4x^2-1)+(2x-1)^2
b)(x+y+z)^2+(x-y)^2+(x-y)^2+(y-z)^2-(x^2+y^2+z^2)
c)(a+b+c)^2-2(a+b+c)(b+c)+(b+c)^2
Rut gon
a,(4x-7)(16x^2+28x+49)
b,(3x+1)(9x^2-3x+1)-9x(3x^2-1)
cho a3+b3=2.tinh gia tri bieu thuc cua a+b
a+b+c=2m thì 4m (m-a)=b^2+c^2-a^2-2bc
