Đáp án:
Giải thích các bước giải:
Bài 2:
a) (3+xy2)2=32+2.3.xy2+(xy2)2(3+xy2)2=32+2.3.xy2+(xy2)2
= 9+6xy2+x2y4=9+6xy2+x2y4
b) (10−2m2n)2=102−2.10.2m2n+(2m2n)2(10−2m2n)2=102−2.10.2m2n+(2m2n)2
= 100−40m2n+4m4n2=100−40m2n+4m4n2
c) (a−b2)(a+b2)=a2−(b2)2=a2−b4(a−b2)(a+b2)=a2−(b2)2=a2−b4
Bài 5:
a) 3012=(300+1)2=3002+2.300.1+123012=(300+1)2=3002+2.300.1+12
= 90000+600+1=90601=90000+600+1=90601
b) 4992=(500−1)2=5002−2.500.1+124992=(500−1)2=5002−2.500.1+12
= 250000−1000+1=249001=250000−1000+1=249001
c) 68.72ư=(70−2).(70+2)=702−22=4900−4=4896
