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3 câu trả lời 853
\[\begin{array}{l}
a){\left( {x - y} \right)^2} + 4xy{\rm{ }}\\
{\rm{ = }}{{\rm{x}}^2} - 2xy + {y^2} + 4xy\\
= {x^2} + 2xy + {y^2}\\
= {(x + y)^2}\\
b){\left( {6x - 2} \right)^2} + 4\left( {3x - 1} \right).\left( {2 + y} \right) + {\left( {y + 2} \right)^2}\\
= 36{x^2} - 24x + 4 + 4(6x + 3xy - 2 - y) + {y^2} + 4y + 4\\
= 36{x^2} - 24x + 4 + 24x + 12xy - 8 - 4y + {y^2} + 4y + 4\\
= 36{x^2} + 12xy + {y^2}\\
= {(6x)^2} + 2.6x.y + {y^2}\\
= {(6x + y)^2}\\
{\rm{ }}c){\left( {x - y} \right)^2} + 2\left( {{x^2} - {y^2}} \right) + {\left( {x + y} \right)^2}\\
= {(x - y)^2} + 2(x - y)(x + y) + {(x + y)^2}\\
= {(x - y + x + y)^2}\\
= {(2x)^2}\\
= 4{x^2}
\end{array}\]
a)(x−y)2+4xy=x2−2xy+y2+4xy=x2+2xy+y2=(x+y)2b)(6x−2)2+4(3x−1).(2+y)+(y+2)2=36x2−24x+4+4(6x+3xy−2−y)+y2+4y+4=36x2−24x+4+24x+12xy−8−4y+y2+4y+4=36x2+12xy+y2=(6x)2+2.6x.y+y2=(6x+y)2c)(x−y)2+2(x2−y2)+(x+y)2=(x−y)2+2(x−y)(x+y)+(x+y)2=(x−y+x+y)2=(2x)2=4x2
a)(x−y)2+4xy=x2−2xy+y2+4xy=x2+2xy+y2=(x+y)2b)(6x−2)2+4(3x−1).(2+y)+(y+2)2=36x2−24x+4+4(6x+3xy−2−y)+y2+4y+4=36x2−24x+4+24x+12xy−8−4y+y2+4y+4=36x2+12xy+y2=(6x)2+2.6x.y+y2=(6x+y)2c)(x−y)2+2(x2−y2)+(x+y)2=(x−y)2+2(x−y)(x+y)+(x+y)2=(x−y+x+y)2=(2x)2=4x2
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