Toán Lớp 7: Tính A+B, A-B, B-A a, A=x ²y+0xy ³-7,5x ³y ²+x ³ B=3xy ³-x ²y+5,5x ³y ² b, A=x ^5+xy+0,3y ²-2 B=x ²y ³+5+1,3y ² c, A=x ²y+xy

Question

Toán Lớp 7:  Tính A+B, A-B, B-A a, A=x ²y+0xy ³-7,5x ³y ²+x ³     B=3xy  ³-x ²y+5,5x ³y ² b, A=x ^5+xy+0,3y ²-2     B=x ²y ³+5+1,3y ²  c, A=x ²y+xy ²-5x ²y ²+x ³      B=3xy ²-x ²y+x ²y ²

tonhu12 · Answer

begin{array}{l} a)A = {x^2}y + 0.x{y^3} - 7,5{x^3}{y^2} + {x^3}    = {x^2}y - 7,5{x^3}{y^2} + {x^3}   B = 3x{y^3} - {x^2}y + 5,5{x^3}{y^2}     Leftrightarrow A + B    = {x^2}y - 7,5{x^3}{y^2} + {x^3} + 3x{y^3} - {x^2}y + 5,5{x^3}{y^2}    =  - 2{x^3}{y^2} + {x^3} + 3x{y^3}   A - B    = {x^2}y - 7,5{x^3}{y^2} + {x^3} -  left( {3x{y^3} - {x^2}y + 5,5{x^3}{y^2}}  right)    = {x^2}y - 7,5{x^3}{y^2} + {x^3} - 3x{y^3} + {x^2}y - 5,5{x^3}{y^2}    = 2{x^2}y - 13{x^3}{y^2} + {x^3} - 3x{y^3}   B - A    = 3x{y^3} - {x^2}y + 5,5{x^3}{y^2} -  left( {{x^2}y - 7,5{x^3}{y^2} + {x^3}}  right)    = 3x{y^3} - {x^2}y + 5,5{x^3}{y^2} - {x^2}y + 7,5{x^3}{y^2} - {x^3}    = 3x{y^3} - 2{x^2}y + 13{x^3}{y^2} - {x^3}   b)A = {x^5} + xy + 0,3{y^2} - 2   B = {x^2}{y^3} + 5 + 1,3{y^2}   A + B    = {x^5} + xy + 0,3{y^2} - 2 + {x^2}{y^3} + 5 + 1,3{y^2}    = {x^5} + xy + 1,6{y^2} + 3 + {x^2}{y^3}   A - B    = {x^5} + xy + 0,3{y^2} - 2 -  left( {{x^2}{y^3} + 5 + 1,3{y^2}}  right)    = {x^5} + xy + 0,3{y^2} - 2 - {x^2}{y^3} - 5 - 1,3{y^2}    = {x^5} + xy - 1{y^2} - 7 - {x^2}{y^3}   B - A    = {x^2}{y^3} + 5 + 1,3{y^2} -  left( {{x^5} + xy + 0,3{y^2} - 2}  right)    = {x^2}{y^3} + 5 + 1,3{y^2} - {x^5} - xy - 0,3{y^2} + 2    = {x^2}{y^3} + 7 + 1{y^2} - {x^5} - xy   c)A = {x^2}y + x{y^2} - 5{x^2}{y^2} + {x^3}   B = 3x{y^2} - {x^2}y + {x^2}{y^2}   A + B    = {x^2}y + x{y^2} - 5{x^2}{y^2} + {x^3} + 3x{y^2} - {x^2}y + {x^2}{y^2}    = 4x{y^2} - 4{x^2}{y^2} + {x^3}   A - B    = {x^2}y + x{y^2} - 5{x^2}{y^2} + {x^3} -  left( {3x{y^2} - {x^2}y + {x^2}{y^2}}  right)    = {x^2}y + x{y^2} - 5{x^2}{y^2} + {x^3} - 3x{y^2} + {x^2}y - {x^2}{y^2}    = 2{x^2}y - 2x{y^2} - 6{x^2}{y^2} + {x^3}   B - A    = 3x{y^2} - {x^2}y + {x^2}{y^2} -  left( {{x^2}y + x{y^2} - 5{x^2}{y^2} + {x^3}}  right)    = 3x{y^2} - {x^2}y + {x^2}{y^2} - {x^2}y - x{y^2} + 5{x^2}{y^2} - {x^3}    = 2x{y^2} - 2{x^2}y + 6{x^2}{y^2} - {x^3}  end{array}