初一数学题,要详细的过程,求代数式的值一直x^2+xy=3 xy+y^2=2,求下列代数式的值,要过程.①x^2-y^2②x^2+4xy+3y^2③2x^2-xy-3y^2
来源:学生作业帮助网 编辑:作业帮 时间:2024/06/21 12:20:39
![初一数学题,要详细的过程,求代数式的值一直x^2+xy=3 xy+y^2=2,求下列代数式的值,要过程.①x^2-y^2②x^2+4xy+3y^2③2x^2-xy-3y^2](/uploads/image/z/1644517-37-7.jpg?t=%E5%88%9D%E4%B8%80%E6%95%B0%E5%AD%A6%E9%A2%98%2C%E8%A6%81%E8%AF%A6%E7%BB%86%E7%9A%84%E8%BF%87%E7%A8%8B%2C%E6%B1%82%E4%BB%A3%E6%95%B0%E5%BC%8F%E7%9A%84%E5%80%BC%E4%B8%80%E7%9B%B4x%5E2%2Bxy%3D3+++xy%2By%5E2%3D2%2C%E6%B1%82%E4%B8%8B%E5%88%97%E4%BB%A3%E6%95%B0%E5%BC%8F%E7%9A%84%E5%80%BC%2C%E8%A6%81%E8%BF%87%E7%A8%8B.%E2%91%A0x%5E2-y%5E2%E2%91%A1x%5E2%2B4xy%2B3y%5E2%E2%91%A22x%5E2-xy-3y%5E2)
初一数学题,要详细的过程,求代数式的值一直x^2+xy=3 xy+y^2=2,求下列代数式的值,要过程.①x^2-y^2②x^2+4xy+3y^2③2x^2-xy-3y^2
初一数学题,要详细的过程,求代数式的值
一直x^2+xy=3 xy+y^2=2,求下列代数式的值,要过程.
①x^2-y^2
②x^2+4xy+3y^2
③2x^2-xy-3y^2
初一数学题,要详细的过程,求代数式的值一直x^2+xy=3 xy+y^2=2,求下列代数式的值,要过程.①x^2-y^2②x^2+4xy+3y^2③2x^2-xy-3y^2
(1)已知x^2+xy=3 xy+y^2=2,两式相减得x^2-y^2=1
(2)x^2+4xy+3y^2=x^2+xy+3(xy+y^2)=3+3*2=9
(3)2x^2-xy-3y^2=2(x^2+xy)-3(xy+y^2)=2*3-3*2=0
x^2+xy=3-----------A
xy+y^2=2-----------B
①A-B得:(x^2+xy)-(xy+y^2)=x^2-y^2=3-2=1
②A+3*B得:(x^2+xy)+3*(xy+y^2)=x^2+4xy+3y^2=3+3*2=9
③2*A-3*B得:2*(x^2+xy)-3*(xy+y^2)=2x^2-xy-3y^2=2*3-3*2=0
(x^2+xy)-(xy+y^2)=x^2-y^2=1
x^2+xy+3(xy+y^2)=x^2+4xy+3y^2=3+6=9
2(x^2+xy)-3(xy+y^2)=2x^2-xy-3y^2=0
x^2-y^2=(3-xy)-(2-xy)=1
x^2+4xy+3y^2==(3-xy)+4xy+3(2-xy)=9
2x^2-xy-3y^2=2(3-xy)-xy-3(2-xy)=0
x^2+xy=3
xy+y^2=2,
x^2-y^2=1
①x^2-y^2=1
②x^2+4xy+3y^2=x^2+xy+3xy+3y^2=3+2*3=9
③2x^2-xy-3y^2=2x^2+2xy-3xy-3y^2=6-6=0