1 习题12.2第1题答案
(
1)
40a5;
(
2)
-132a23;
(
3)
162x6;
(
4)
x4y2.
2 习题12.2第2题答案
解:
2.5×
103×
2.3×
106=5.75×
109(千克),
即总重约为
5.75×
109千克.
3 习题12.2第3题答案
解:(
1)
-3x·(
2x2-x+4)
=-3x·
2x2+3x·
x-3x·
4
=-6x3+3x2-12x.
(
2)
5/2xy·
(
-x3y2+ 4/5x2y3)
=5/2xy·
x3y2 +5/2xy·
4/5x2y3
=5/2 x4y3+2x3y4.
4 习题12.2第4题答案
解:(
1)(
1/2x+1)
-3x(
3/2x-2)
=1/2x2+x-9/2x2+6x-4x2+7x.
(
2)
y2(
y-1)
+2y(
y2-2y+3)
=y3-y2+2y3-4y2+6y
=3y3-5y2+6y.
5 习题12.2第5题答案
(
1)(
x+5)(
x-6)
=x2-6x+5x-30=x2-x=30.
(
2)
(
2x+1)(
2x+3)
=4x2+6x+2x+3
= 4x2+8x+3.
(
3)(
3x+4)
(
3x-4)
=9x2-12x+12x-16
=9x2-16.
(
4)(
9x+4y)
2
=(
9x+4y)(
9x+4y)
=81x2+36xy+36xy+16y2
= 81x2+72xy+16y2.
6 习题12.2第6题答案
解:(
1)(
3x-1)(
2x2+3x-4)
=6x3+9x2-12x-2x2-3x+4
=6x3+7x2-15x+4.
(
2)(
x+2y)(
x2-2xy+4y2)
=x3-2x2y+4xy2+2x2y-4xy2+8y3
=x3+8y3.