因式分解x^2+3xy+2y^2+4x+5y+3 由于x^2+3xy+2y^2=(x+2y)(X+y),而4x+5y拆为x+2y和3(x+y),而3=1乘3由十字相乘法,可得原式=(x+2y+3)(x+y+1)但我看不懂【由十字相乘法,可得原式=(x+2y+3)(x+y+1)】,
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![因式分解x^2+3xy+2y^2+4x+5y+3 由于x^2+3xy+2y^2=(x+2y)(X+y),而4x+5y拆为x+2y和3(x+y),而3=1乘3由十字相乘法,可得原式=(x+2y+3)(x+y+1)但我看不懂【由十字相乘法,可得原式=(x+2y+3)(x+y+1)】,](/uploads/image/z/601503-15-3.jpg?t=%E5%9B%A0%E5%BC%8F%E5%88%86%E8%A7%A3x%5E2%2B3xy%2B2y%5E2%2B4x%2B5y%2B3+%E7%94%B1%E4%BA%8Ex%5E2%2B3xy%2B2y%5E2%3D%28x%2B2y%29%28X%2By%EF%BC%89%2C%E8%80%8C4x%2B5y%E6%8B%86%E4%B8%BAx%2B2y%E5%92%8C3%EF%BC%88x%2By%EF%BC%89%2C%E8%80%8C3%3D1%E4%B9%983%E7%94%B1%E5%8D%81%E5%AD%97%E7%9B%B8%E4%B9%98%E6%B3%95%2C%E5%8F%AF%E5%BE%97%E5%8E%9F%E5%BC%8F%3D%EF%BC%88x%2B2y%2B3%EF%BC%89%EF%BC%88x%2By%2B1%EF%BC%89%E4%BD%86%E6%88%91%E7%9C%8B%E4%B8%8D%E6%87%82%E3%80%90%E7%94%B1%E5%8D%81%E5%AD%97%E7%9B%B8%E4%B9%98%E6%B3%95%2C%E5%8F%AF%E5%BE%97%E5%8E%9F%E5%BC%8F%3D%EF%BC%88x%2B2y%2B3%EF%BC%89%EF%BC%88x%2By%2B1%EF%BC%89%E3%80%91%2C)
因式分解x^2+3xy+2y^2+4x+5y+3 由于x^2+3xy+2y^2=(x+2y)(X+y),而4x+5y拆为x+2y和3(x+y),而3=1乘3由十字相乘法,可得原式=(x+2y+3)(x+y+1)但我看不懂【由十字相乘法,可得原式=(x+2y+3)(x+y+1)】,
因式分解x^2+3xy+2y^2+4x+5y+3 由于x^2+3xy+2y^2=(x+2y)(X+y),而4x+5y拆为x+2y和3(x+y),而3=1乘3
由十字相乘法,可得原式=(x+2y+3)(x+y+1)
但我看不懂【由十字相乘法,可得原式=(x+2y+3)(x+y+1)】,
因式分解x^2+3xy+2y^2+4x+5y+3 由于x^2+3xy+2y^2=(x+2y)(X+y),而4x+5y拆为x+2y和3(x+y),而3=1乘3由十字相乘法,可得原式=(x+2y+3)(x+y+1)但我看不懂【由十字相乘法,可得原式=(x+2y+3)(x+y+1)】,
[(x+2y)+3]* [(x+y)+1]你把小括号先看成整体.这样不就好理解了
x^2+3xy+2y^2+4x+5y+3
= x^2+(2+1)xy+2y^2+4x+5y+3
=x^2+2xy+xy+2y^24x+5y+3
=x(x+2y)+y(x+2y)+4x+5y+3
= (x+y)(x+2y)+4x+5y+3
=(x+y)(x+2y)+x+2y+3x+3y+3
=(x+y)(x+2y)+(x+2y)+3(x+y+1)
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x^2+3xy+2y^2+4x+5y+3
= x^2+(2+1)xy+2y^2+4x+5y+3
=x^2+2xy+xy+2y^24x+5y+3
=x(x+2y)+y(x+2y)+4x+5y+3
= (x+y)(x+2y)+4x+5y+3
=(x+y)(x+2y)+x+2y+3x+3y+3
=(x+y)(x+2y)+(x+2y)+3(x+y+1)
=(x+y+1)(x+2y)+3(x+y+1)
=(x+y+1)(x+2y+3)
x^2+3xy+2y^2
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