Question

BT13: Cho\(A=16x^4-8x^3y+7x^2y^2-9y^4\),\(B=-15x^4+3x^3y-5x^2y^2-6y^4\) và \(C=5x^3y+3x^2y^2+17y^4+1\)

a, Tính A+B-C

b, Tính A-C+B

Answer 1

\(a,A+B-C=16x^4-8x^3y+7x^2y^2-9y^4-15x^4+3x^3y-5x^2y^2-6y^4-5x^3y-3x^2y^2-17y^4-1\)

\(=\left(16x^4-15x^4\right)+\left(-8x^3y+3x^3y-5x^3y\right)+\left(7x^2y^2-5x^2y^2-3x^2y^2\right)+\left(-9y^4-6y^4-17y^4\right)-1\)

\(=x^4-10x^3y-x^2y^2-32y^4-1\)

\(b,A-C+B=A+B-C\) ( giống câu a )

Answer 2

\(a,\)

\(A+B+C\)

\(=16x^4-8x^3y+7x^2y^2-9y^4-15x^4+3x^3y-5x^2y^2-6y^4-\left(5x^3y+3x^2y^2+17y^4+1\right)\)

\(=16x^4-8x^3y+7x^2y^2-9y^4-15x^4+3x^3y-5x^2y^2-6y^4-5x^3y-3x^2y^2-17y^4-1\)

\(=\left(16x^4-15x^4\right)+\left(-9y^4-6y^4-17y^4\right)+\left(-8x^3y+3x^3y-5x^3y\right)+\left(7x^2y^2-5x^2y^2-3x^2y^2\right)-1\)

\(=x^4-32y^4-10x^3y-x^2y^2-1\)

\(b,\)

\(A-C+B=A+B-C=x^4-32y^4-10x^3y-x^2y^2-1\)

Answer 3

a: A+B-C

=16x^4-8x^3y+7x^2y^2-9y^4-15x^4+3x^3y-5x^2y^2-6y^4-C

=x^4-5x^3y+2x^2y^2-15y^4-5x^3y-3x^2y^2-17y^4-1

=x^4-10x^3y-x^2y^2-32y^4-1

b: A-C+B=A+B-C=x^4-10x^3y-x^2y^2-32y^4-1

Answer 4

`@` `\text {Ans}`

`\downarrow`

`a,`

`A+B-C`

`=`\(\left(16x^4-8x^3y+7x^2y^2-9y^4\right)+\left(-15x^4+3x^3y-5x^2y^2-6y^4\right)\)

\(-\left(5x^3y+3x^2y^2+17y^4+1\right)\)

`=`\(16x^4-8x^3y+7x^2y^2-9y^4-15x^4+3x^3y+-5x^2y^2-6y^4-5x^3y\)

\(-3x^2y^2-17y^4-1\)

`=`\(\left(16x^4-15x^4\right)\) \(+\) \((-8x^3y+3x^3y-5x^3y)\) \(+ (7x^2y^2 - 5x^2y^2 - 3x^2y^2)\)\(+ (-9y^4-6y^4-17y^4)-1\)

`= x^4 - 10x^3y -x^2y^2 - 32y^4 - 1`

`b,`

`A-C+B`

`=`\((16x^4-8x^3y + 7x^2y^2 - 9y^4)-(5x^3y+3x^2y^2+17y^4+1)\)`+`\((-15x^4+3x^3y-5x^2y^2-6y^4 )\)

`=`\(16x^4-8x^3y + 7x^2y^2 - 9y^4-5x^3y-3x^2y^2-17y^4-1\)\(-15x^4+3x^3y-5x^2y^2-6y^4 \)

`=`\((16x^4-15x^4)+(-8x^3y-5x^3y+3x^3y)+(7x^2y^2-3x^2y^2-5x^2y^2)\)

\((-9y^4-17y^4-6y^4)\)

`=  x^4 - 10x^3y -x^2y^2 - 32y^4 - 1`