Question

a= 3x2 - 9xy + y2 -7 b= -y2 - 3x +12

a) tính a+b

b) tính a-b

Answer 1

a) Ta có:

\(A+B\)

\(=3x^2-9xy+y^2-7-y^2-3x+12\)

\(=3x^2-9xy+5-3x\)

b) Ta có:

\(A-B\)

\(=\left(3x^2-9xy+y^2-7\right)-\left(-y^2-3x+12\right)\)

\(=3x^2-9xy+y^2-7+y^2+3x-12\)

\(=3x^2-9xy+2y^2+3x-19\)

Answer 2

a) \(a+b=\left(3x^2-9xy+y^2\right)+\left(-y^2-3x+12\right)\)

\(=3x^2-9xy+y^2-y^2-3x+12\)

\(=3x^2-9xy+\left(y^2-y^2\right)-3x+12\)

\(=3x^2-9xy-3x+12\)

b) \(a-b=\left(3x^2-9xy+y^2\right)-\left(-y^2-3x+12\right)\)

\(=3x^2-9xy+y^2+y^2+3x-12\)

\(=3x^2-9xy+\left(y^2+y^2\right)+3x-12\)

\(=3x^2-9xy+2y^2+3x-12\)