因式分解:1)0.49(x+y)^2= 2)36分之1(m-n)^2= 3)已知x+y=5,求代数式x^2-y^2+10y的值

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因式分解:1)0.49(x+y)^2= 2)36分之1(m-n)^2= 3)已知x+y=5,求代数式x^2-y^2+10y的值

因式分解:1)0.49(x+y)^2= 2)36分之1(m-n)^2= 3)已知x+y=5,求代数式x^2-y^2+10y的值
因式分解:1)0.49(x+y)^2= 2)36分之1(m-n)^2= 3)已知x+y=5,求代数式x^2-y^2+10y的值

因式分解:1)0.49(x+y)^2= 2)36分之1(m-n)^2= 3)已知x+y=5,求代数式x^2-y^2+10y的值
1.0·49(x+y)²
=49(x+y)²/100
= 【 7/10(x+y)】²
2.1/36(m-n)²
=[1/6(m-n)]²
3 .x²-y²+10y
=(x+y)(x-y)+10y
将x+y=5代入上式有
(x+y)(x-y)+10y
=5(x-y)+10y
=5x-5y+10y
=5(x+y)
=5×5
=25

前两个因式分解没懂。第三个x+y=5,即x=5-y,代入代数式得25.

1. 0·49(x+y)²
=49(x+y)²/100
= 【 7/10(x+y)】²
2. 1/36(m-n)²
=[1/6(m-n)]²
3 .x²-y²+10y
=(x+y)(x-y)+10y
将x+y=5代入上式有
(x+y)(x-y)+10y<...

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1. 0·49(x+y)²
=49(x+y)²/100
= 【 7/10(x+y)】²
2. 1/36(m-n)²
=[1/6(m-n)]²
3 .x²-y²+10y
=(x+y)(x-y)+10y
将x+y=5代入上式有
(x+y)(x-y)+10y
=5(x-y)+10y
=5x-5y+10y
=5(x+y)
=5×5
=25

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