Ha's grandmother told us about her life in the past. She đin't go to school (1)..................she had to look after her sisters and brothers. She used to help (2).............parents with the housework. She had to do(3).............without the help of the modern equipment because there was no electricity at that(4).......................Life was quite hard for her
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a) 1km2 200dam2 = 102ha
240000m2 = 24ha
b)12km2 3hm2 = 1203ha
12400dam2 = 124ha
c) 123km2 400dam2 = 12304ha
500000m2 = 50ha
d) 5hm2 70000m2 = 12ha
246000000dm2 = 246ha
a) x4+x3+2x2+x+1=(x4+x3+x2)+(x2+x+1)=x2(x2+x+1)+(x2+x+1)=(x2+x+1)(x2+1)
b)a3+b3+c3-3abc=a3+3ab(a+b)+b3+c3 -(3ab(a+b)+3abc)=(a+b)3+c3-3ab(a+b+c)
=(a+b+c)((a+b)2-(a+b)c+c2)-3ab(a+b+c)=(a+b+c)(a2+2ab+b2-ac-ab+c2-3ab)=(a+b+c)(a2+b2+c2-ab-ac-bc)
c)Đặt x-y=a;y-z=b;z-x=c
a+b+c=x-y-z+z-x=o
đưa về như bài b
d)nhóm 2 hạng tử đầu lại và 2hangj tử sau lại để 2 hạng tử sau ở trong ngoặc sau đó áp dụng hằng đẳng thức dề tính sau đó dặt nhân tử chung
e)x2(y-z)+y2(z-x)+z2(x-y)=x2(y-z)-y2((y-z)+(x-y))+z2(x-y)
=x2(y-z)-y2(y-z)-y2(x-y)+z2(x-y)=(y-z)(x2-y2)-(x-y)(y2-z2)=(y-z)(x2-2y2+xy+xz+yz)
MK làm nè :
câu 1 : 2,450ha
câu 2 : 3,0059 ha
Câu 3 : 4,0005 ha
Câu 4 : 1,234 ha
Câu 5 : 1,025 ha
Câu 6 : 2,003 ha
Mk làm sai thì ko Tích nha , làm đúng thì xin bạn tích mk !
Ha's grandmother told us about her life in the past. She đin't go to school (1)........because..........she had to look after her sisters and brothers. She used to help (2)......her.......parents with the housework. She had to do(3).......it......without the help of the modern equipment because there was no electricity at that(4)...........time............Life was quite hard for her