Question

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Answer 1

Bài 1:

1: \(5x^2\cdot3xy^2=\left(5\cdot3\right)\cdot\left(x^2\cdot x\right)\cdot y^2=15x^3y^2\)

Hệ số là 15

Bậc là 3+2=5

2: \(4x^2\cdot\left(-4xy^2\right)=4\cdot\left(-4\right)\cdot x^2\cdot x\cdot y^2=-16x^3y^2\)

Hệ số là -16

Bậc là 3+2=5

3: \(-x^2y^5\cdot\left(-xy\right)=\left(-1\right)\cdot\left(-1\right)\cdot x^2\cdot x\cdot y^5\cdot y=x^3y^6\)

bậc là 3+6=9

Hệ số là 1

Bài 2:

a: \(A=\frac13x^2y+xy^2-xy+\frac12xy^2-5xy-\frac13x^2y\)

\(=\left(\frac13x^2y-\frac13x^2y\right)+\left(xy^2+\frac12xy^2\right)+\left(-xy-5xy\right)=\frac32xy^2-6xy\)

\(=xy\left(\frac32y-2\right)\)

Khi x=1/2;y=1 thì \(A=\frac12\cdot1\cdot\left(\frac32\cdot1-2\right)=\frac12\cdot\left(-\frac12\right)=-\frac14\)

b: \(B=\frac12xy^2+\frac23x^2y-xy+xy^2-\frac13x^2y+2xy\)

\(=\left(\frac12xy^2+xy^2\right)+\left(\frac23x^2y-\frac13x^2y\right)+\left(-xy+2xy\right)=\frac32xy^2+\frac13x^2y+xy\)

Khi x=1/2;y=1 thì \(B=3\cdot\frac12\cdot1^2+\frac13\cdot\left(\frac12\right)^2\cdot1+\frac12\cdot1=\frac32+\frac{1}{12}+\frac12=2+\frac{1}{12}=\frac{25}{12}\)