计算:(1)[(x+y)2-y(2x+y)-8x]÷2x;(2)已知:m-n=4,m2-n2=24,求(m+n)3的值.(3)已知-2x3m
计算:(1)[(x+y)2-y(2x+y)-8x]÷2x;(2)已知:m-n=4,m2-n2=24,求(m+n)3的值.(3)已知-2x3m+1y2n与7xn-6y-3-...
计算:(1)[(x+y)2-y(2x+y)-8x]÷2x;(2)已知:m-n=4,m2-n2=24,求(m+n)3的值.(3)已知-2x3m+1y2n与7xn-6y-3-m的积与x4y是同类项,求m2+n的值.(4)先化简,再求值:(-2a4x2+4a3x3-34a2x4)÷(-a2x2),其中a=12,x=-4.(5)分解因式:①(x+y)2-9y2;②10b(x-y)2-5a(y-x)2;③(ab+b)2-(a+1)2;
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(1)[(x+y)2-y(2x+y)-8x]÷2x=(x2+2xy+y2-2xy-y2-8x)÷2x=(x2-8x)÷2x=
x?4;
(2)∵m-n=4,m2-n2=24,
∵m2-n2=(m-n)(m+n)=4(m+n)=24,
∴m+n=6,
∴(m+n)3,=63=216;
(3)-2x3m+1y2n?7xn-6y-3-m=-14x3m+n-5y2n-3-m;
∵-2x3m+1y2n与7xn-6y-3-m的积与x4y是同类项,
∴
,
解得:
,
∴m2+n=22+3=7;
(4)(-2a4x2+4a3x3-
a2x4)÷(-a2x2)=2a2-4ax+
x2,
当a=
,x=-4时,原式=2×(
)2-4×
×(-4)+
×(-4)2=
;
(5)①(x+y)2-9y2=(x+y+3y)(x+y-3y)=(x+4y)(x-2y);
②10b(x-y)2-5a(y-x)2=10b(x-y)2-5a(x-y)2=5(x-y)2(2b-a);
③(ab+b)2-(a+1)2=(ab+b+a+1)(ab+b-a-1).
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2 |
(2)∵m-n=4,m2-n2=24,
∵m2-n2=(m-n)(m+n)=4(m+n)=24,
∴m+n=6,
∴(m+n)3,=63=216;
(3)-2x3m+1y2n?7xn-6y-3-m=-14x3m+n-5y2n-3-m;
∵-2x3m+1y2n与7xn-6y-3-m的积与x4y是同类项,
∴
|
解得:
|
∴m2+n=22+3=7;
(4)(-2a4x2+4a3x3-
3 |
4 |
3 |
4 |
当a=
1 |
2 |
1 |
2 |
1 |
2 |
3 |
4 |
41 |
2 |
(5)①(x+y)2-9y2=(x+y+3y)(x+y-3y)=(x+4y)(x-2y);
②10b(x-y)2-5a(y-x)2=10b(x-y)2-5a(x-y)2=5(x-y)2(2b-a);
③(ab+b)2-(a+1)2=(ab+b+a+1)(ab+b-a-1).
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