Toán Lớp 6: ko tính tổng,hãy giải thích:
3^3+3^4+3^5+3^6 chia hết cho 4
5^5+5^6+5^7+5^8 chia hết cho 6
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Toán Lớp 6: ko tính tổng,hãy giải thích:
3^3+3^4+3^5+3^6 chia hết cho 4
5^5+5^6+5^7+5^8 chia hết cho 6
Comments ( 2 )
3^3 + 3^4+3^5+3^6
= (3^3 + 3^4) + (3^5+3^6)
= 3^3 .( 1+3) + 3^5 . ( 1+3)
= 3^3 . 4 + 3^5 .4
= 4 . (3^3 + 3^5)
=> 3^3 + 3^4+3^5+3^6 $\vdots$ hết cho 4
5^5 + 5^6 +5^7+5^8
= (5^5 + 5^6) + (5^7+5^8)
= 5^5 .( 1+5) + 5^7 . ( 1+5)
= 5^5 . 6 + 5^7 . 6
= 6 . (5^5 + 5^7)
=>5^5 + 5^6 +5^7+5^8 $\vdots$ hết cho 6
Giải đáp:
3^3+3^4+3^5+3^6
=(3^3+3^4)+(3^5+3^6)
=3^3(1+3)+3^5(1+3)
=(3^3+3^5)(1+3)
=(3^3+3^5).4
Mà 4 $\vdots$ 4
⇒3^3+3^4+3^5+3^6 $\vdots$ 4
5^5+5^6+5^7+5^8
=(5^5+5^6)+(5^7+5^8)
=5^5(1+5)+5^7(1+5)
=(5^5+5^7)(1+5)
=(5^5+5^7).6
Mà 6 $\vdots$ 6
⇒5^5+5^6+5^7+5^8 $\vdots$ 6