Bài tập theo tuần Toán 8 - Tuần 13

2514x2y;1421xy5

Nhân tử phụ:

42x2y5:14x2y=3y442x2y5:21xy5=2x

Quy đồng:

2514x2y=25.3y442x2y5=75y442x2y51421xy5=14.2x42x2y5=28x42x2y5

4x−42xx+3;x−33xx−3; MTC:6xx+3x−3

Nhân tử phụ:

6xx+3x−3:2xx+3=3x−36xx+3x−3:3xx−3=2x+3

Quy đồng:

4x−42xx+3=4x−4.3x−36xx+3x−3=12x2−48x+366xx+3x−3x−33xx−3=x−3.2.x+33xx−3.2x+3=2x2−186xx+3x−3

2xx+23;x−22xx+22, MTC: 2xx+23

Nhân tử phụ:

2xx+23:x+23=2x2xx+23:2xx+22=x+2

Quy đồng:

2xx+23=2x.2x2xx+23=4x22xx+23x−22xx+22=x−2x+22xx+22=x2−42xx+22

5x2x3+6x2+12x+8;4x2+4x+4;32x+4

Hay 5x2x+23;4x+22;32x+2. MTC:2x+23

Nhân tử phụ:

2x+23:x+23=22x+23:x+22=2x+22x+23:2x+2=x+22

Quy đồng:

5x2x+23=5x2.22x+23=10x22x+234x+22=4.2x+22x+23=8x+22x+2332x+2=3x+222x+23

Q=x10−x8+x7+x6+x5+x4−x3−x2+1x30+x24+x18+x12+x6+1=x10−x8+x6−x7−x5+x3+x4−x2+1x18x12+x6+1+x12+x6+1=x4−x2+1x6−x3+1x12+x6+1x18+1=x4−x2+1x6−x3+1x12+2x6+1−x6x6+1x12−x6+1

=x4−x2+1x6−x3+1x6+1−x6x2+1x4−x2+1x12−x6+1

=x6−x3+1x6+x3+1x6−x3+1x2+1x12−x6+1=1x6+x3+1x2+1x12−x6+1