Question

1) Thực hiên phép tính

a)(\(x\)²-2\(x\)+3)(1\(x\)-5)

b)(\(x\)²-2\(x\)\(y\)+\(y\)²)(\(x\)-\(y\))

c)(\(\dfrac{1}{2}\)\(x\)+\(y\))(\(\dfrac{1}{2}\)\(x\)+\(y\))

d)(\(x\)-\(\dfrac{1}{2}\)\(y\))(\(x\)-\(\dfrac{1}{2}\)\(y\))

2) Tính giá trị của biểu thức

a) \(x\)(\(x\)-\(y\))+\(y\)(\(x\)+y) tại \(x\)=6;\(y\)=3

Answer 1

2:

a: Đặt A=\(x\left(x-y\right)+y\left(x+y\right)\)

\(=x^2-xy+xy+y^2=x^2+y^2\)

Khi x=6 và y=3 thì \(A=6^2+3^2=36+9=45\)

Bài 1:

a: \(\left(x^2-2x+3\right)\left(x-5\right)\)

\(=x^3-5x^2-2x^2+10x+3x-15\)

\(=x^3-7x^2+13x-15\)

b: \(\left(x^2-2xy+y^2\right)\left(x-y\right)\)

\(=x^3-x^2y-2x^2y+2xy^2+xy^2-y^3\)

\(=x^3-3x^2y+3xy^2-y^3\)

c: \(\left(\dfrac{1}{2}x+y\right)\left(\dfrac{1}{2}x+y\right)\)

\(=\dfrac{1}{4}x^2+\dfrac{1}{2}xy+\dfrac{1}{2}xy+y^2\)

\(=\dfrac{1}{4}x^2+xy+y^2\)

d: \(\left(x-\dfrac{1}{2}y\right)\left(x-\dfrac{1}{2}y\right)=x^2-\dfrac{1}{2}xy-\dfrac{1}{2}xy+\dfrac{1}{4}y^2\)

\(=x^2-xy+\dfrac{1}{4}y^2\)