课前预习
1、不变;相减
2、a
m-n;≠0
课堂探究
【例1】思路导引答案:
1、单项式多项式
2、(x-2y)²
解:(1)a⁶÷a² =a⁶-2 =a⁴
(2)(-b)⁸÷(-b)=(-b)⁸⁻¹=(-b)⁷=-b⁷.
(3)(ab)⁴÷(ab)²=(ab)⁴⁻²=(ab)² =a²b².
(4) (x-2y)⁴÷(2y -x)²÷(x-2y)
=(x-2y)⁴÷(x-2y)²÷(x-2y)
=(x- 2y)⁴-2-1
=x-2y.
变式训练1-1:B
变式训练1-2:
解:(1)原式=a
(2m+4)-(m-2)=a
m+6.
(2)原式=(x- 2y)³÷(x-2y)² =x-2y.
(3)原式=(a-b)³÷[-(a-b)]
= -(a-b)³⁻¹=-(a-b)².
【例2】思路导引答案:
1、a
m/a
n
2、(a
m)³
解:(1)a
m-n= a
m/a
n=3/5.
(2)a
3m-2n-2=a
3m/a
2n
=(a
m)³/(a
n)²
=3³/5²=27/25
变式训练2-1:A
变式训练2-2:
解:∵10
a÷10
b=10
a-b=20÷1/5=10²,
∴a-b=2.∴3
a÷3
b =3
a-b=3²=9.
课堂训练
1~4:B;A;D;D
5、解:由题意知(b-a)ⁿ=(a-b)ⁿ,故行为偶数,
m-n=1.由m,n小于5,得m=3,n=2.
课后提升
6、 x³
7、 6
8、 100
9、解 : (1) ( -2m² )³ +m⁷÷m= - 8m⁶+m⁶6= - 7m⁶
(2)x³ ·(2x³)²÷ (x-4)² =x³·4x⁶÷x⁸ =4x-3+6-8=4x.
(3) (a-b)¹º÷ (b-a)³÷ (b-a)³
= (b-a)¹º÷ (b-a)³÷ (b-a)³
= (b-a)
10⁻3-3
=(b-a)⁴
10、解:(x
m÷x
2n)³÷x
m-n=(x
m-2
n)³÷x
m-n
=x
3m-6n÷x
m-n
= x
2m-5n.
因为它与4x²是同类项,所以2m-5n=2,
又2m+5n=7,
所以4m²-25n²
=(2m-5n)(2m+5n)
=2×7=14.