288 lượt thi
21 câu hỏi
45 phút
Câu 1:
8xy3x−1312x31−3x=−8xy1−3x312x31−3x=−2y1−3x23x2
Câu 2:
9−x+52x2+4x+4=32−x+52x+22=3−x−53+x+5x+22=−x+2x+8x+22=−x−8x+2
Câu 3:
x2−xy−x+yx2+xy−x−y=xx−y−x−yxx+y−x+y=x−1x−yx−1x+y=x−yx+y
Câu 4:
2a2−2abac+ad−bc−bd=2aa−ba−bc+d=2ac+d
Câu 5:
4x−69+5x+69=9x9=x
Câu 6:
x+3x+xx−3+9x2−3x=x+3x−3+x2+9xx−3=2x2xx−3=2xx−3
Câu 7:
x−1x3−x+1x3−x2+3x3−2x2+x=x−1x3−x+1x2x−1+3xx−12=x3−3x2+3x−1−x3+x+3x2x3x−1=4x−1x3x−1
Câu 8:
x3+x2−2x−20x2−4−5x+2+3x−2=x3+x2−2x−20−5x−2+3x+2x−2x+2=x3+x2−4x−4x−2x+2=x+1x2−4x2−4=x+1
Câu 9:
3x5x+5y−x10x−10y=3x5x+y−x10x−y=6x(x−y)−xx+y10(x+y)x−y=5x2−5xy10x+yx−y=5xx−y10x+yx−y=x2x+y
Câu 10:
32x2+2x+2x−1x2−1−2x=32xx+1+2x−1x−1x+1−2x=3x−3+4x2−2x−4x2+42xx−1x+1=x+12xx−1x+1=22xx−1
Câu 11:
x2+2x3−1+2x2+x+1+11−x=x2+2+2x−2−x2−x−1x−1x2+x+1=x−1x−1x2+x+1=1x2+x+1
Câu 12:
x+12x−2+3x2−1−x+32x+2.4x2−45=x+12x−1+3x−1x+1−x+32x+1.4x2−15=x2+2x+1+6−x2−2x+32x−1x+1.4x−1x+15=10.42.5=4
Câu 13:
6x+7x2+7x−5x+7=6x+7−5xxx+7=x+7xx+7=1x
Câu 14:
x2−362x+10.26−x=x−6x+6.2−2x+5x−6=−x−6x+5
Câu 15:
1x2+x−2−xx+1:1x+x−2=1+x2−2xxx+1:x2−2x+1x=x2−2x+1xx+1.xx2−2x+1=1x+1
Câu 16:
4x2−3x+17x3−1+2x−1x2+x+1+6xx−x2=4x2−3x+17+2x2−3x+1x−1x2+x+1+61−x=6x2−6x+18x−1x2+x+1−6x2+x+1x−1x2+x+1=−12x+12x−1x2+x+1=−12x−1x−1x2+x+1=−12x2+x+1
Câu 17:
xx2−36−x−6x2+6x:2x−6x2+6x+x6−x=x2−x−62x−6x+6x.xx+62x−3−xx−6=x−x+6x+x−6x−6.2.x−3−xx−6=6.2.x−32x−3x−6−xx−6=6x−6−xx−6=6−xx−6=−1
Câu 18:
x2+xx2+x+1−2x3+x2−xx3−1−2−1x−1:2x−1x−x2=x2+xx2+x+1−2x3+x2−x−2x3+2−x2−x−1x−1x2+x+1.−xx−12x−1=x2+xx2+x+1−−2x+1.−xx2+x+1.2x−1=x2+xx2+x+1+−xx2+x+1=x2x2+x+1
Câu 19:
x2+4x2x2−4.x+22x−4+2−3xx3−4x.x2−4x−2=x4−4x2+4x2x+2x−2.x+22x−2+2−3xxx−2=x4x+2x−2.x2+2x+4−6x2xx−2=x3.x−222.(x+2)x−2=x3.x−22x+2
Câu 20:
a) x≠0, x≠−5
b) B=x2+2x2x+10+x−5x+50−5x2xx+5=xx+22x+5+x−5x+50−5x2xx+5=x3+2x2+x−5x+5+50−5x2xx+5=x3+3x2−5x+252xx+5=x2(x+5)−2x(x+5)+5(x+5)2xx+5=x+5x2−2x+52xx+5=x2−2x+52x
B=0⇔x2−2x+52x=0⇔x2−2x+5=0 (vô lý vì x2−2x+5=(x−1)2+4>0)
B=14⇔x2−2x+52x=14⇔4x2−10x+20=0(VN)
Câu 21:
EH=a−b⇒SAEB=ca−b2SABCD=cb⇒SABCDE=SAEB+SABCD=ca−cb2+cb=ca−cb+2cb2=ca+cb2=ca+b2