Câu 1 tính
A (-15)+14+(-85)
Câu 2 tìm x
a 12x-64=2^5
b x-7=(-14)+(-8)
Câu 3
Cho S =1+2+2^2+2^3+2^4+2^5+2^6+2^7
Câu 1 tính A (-15)+14+(-85) Câu 2 tìm x a 12x-64=2^5 b x-7=(-14)+(-8) Câu 3 Cho S =1+2+2^2+2^3+2^4+2^5+2^6+2^7
By Mary
By Mary
Câu 1 tính
A (-15)+14+(-85)
Câu 2 tìm x
a 12x-64=2^5
b x-7=(-14)+(-8)
Câu 3
Cho S =1+2+2^2+2^3+2^4+2^5+2^6+2^7
Đáp án:
`a) (-15)+14+(-85)=[(-15)+(-85)]+14=-100+14=-86`
`——`
`12x-64=2^5 `
`-> 12x-64=32`
`-> 12x=32+64=96`
`-> x=96:12=8`
`—–`
`x-7=(-14)+(-8)`
`-> x-7=-22`
`-> x=-22+7`
`-> x=-15`
`—–`
`S =1+2+2^2+2^3+2^4+2^5+2^6+2^7`
`=(1+2)+(2^2+2^3)+(2^4+2^5)+(2^6+2^7)`
`=3+2^2(1+2)+2^4(1+2)+2^6(1+2)`
`=3+2^2. 3+2^4. 3+2^6. 3`
`=3(1+2^2+2^4+2^6) vdots 3`
Đáp án:
Câu 1:
A= (-15)+14+(-85)
A=(-1) + (-85)
A=(-86)
Câu 2:
a, 12x – 64 =2^5
12x – 64 = 32
12x = 32+64
12x = 96
x = 96:12
x = 8
Vậy x = 8
b,x-7= (-14)+(-8)
x-7= (-22)
x = (-22)+7
x = (-15)
Vậy x = (-15)
Câu 3:
S = 1+2+2^2+2^3+2^4+2^5+2^6+2^7
S = (1+2) +2^2×(1+2^1)+2^4×(1+2^1)+2^6×(1+2^1)
S = 3 × 1+ 2^2 × 3 +2^4 ×3 + 2^6 × 3
S = 3 × (1+2^2 + 2^4 + 2^6) chia hết cho 3
Hay S =( 1+2+2^2+2^3+2^4+2^5+2^6+2^7 ) chia hết cho 3
Vậy S =( 1+2+2^2+2^3+2^4+2^5+2^6+2^7 ) chia hết cho 3