Câu hỏi của tranyennhi

Question

1 tính

a. ( 29.16+29.34):210

b.(34.57-92.21):35

c.A=3+32+33+.....+319\

2 xét xem tổng hiệu sau nào sau dây chi hết cho 4

a. 44+66+72

b.58-20+18

c.2.5.4.11-56

3 tìm chữ số a;b để

a...

Thư Huỳnh · Accepted Answer

Bài 1: a/ $\left(2^9.16+2^9.34\right):2^{10}$$=2^9.\left(16+34\right):2^{10}$$=50.2^9:2^{10}$$=50.2^9:2^9:2=50.\dfrac{1}{2}=25$

c/ $A=3+3^2+3^3+...+3^{19}$

$3A=3^2+3^3+3^4+...+3^{20}$

$3A-A=\left(3^2+3^3+3^4+...+3^{20}\right)-\left(3+3^2+3^3+...+3^{19}\right)$

$2A=3^{20}-3$

$A=\left(3^{20}-3\right):2$

b/$\left(3^4.57-9^2.21\right):3^5=\left(3^4.57-3^4.21\right):3^5=3^4.\left(57-21\right):3^5=3^4:3^5.36=3^4:3^4:3.36=\dfrac{1}{3}.36=12$Câu trả lời: Bài 1: a/ $\left(2^9.16+2^9.34\right):2^{10}$$=2^9.\left(16+34\right):2^{10}$$=50.2^9:2^{10}$$=50.2^9:2^9:2=50.\dfrac{1}{2}=25$

c/ $A=3+3^2+3^3+...+3^{19}$

$3A=3^2+3^3+3^4+...+3^{20}$

$3A-A=\left(3^2+3^3+3^4+...+3^{20}\right)-\left(3+3^2+3^3+...+3^{19}\right)$

$2A=3^{20}-3$

$A=\left(3^{20}-3\right):2$

b/$\left(3^4.57-9^2.21\right):3^5=\left(3^4.57-3^4.21\right):3^5=3^4.\left(57-21\right):3^5=3^4:3^5.36=3^4:3^4:3.36=\dfrac{1}{3}.36=12$

Thư Huỳnh · Answer

Bài 2:

a/ 44 + 66 + 72

Vì 44 $⋮$ 4     :        72 $⋮$ 4       và    66 $⋮̸$ 4

nên tổng ( 44 + 66 + 72 ) $⋮̸$ 4

b/ 58 - 20 +18

Vì 58 + 18 = 76 $⋮$ 4        và       20 $⋮$ 4

nên ( 58 - 20 + 18 ) $⋮$ 4

c/ 2.5.4.11 - 56

Vì ( 2.5.4.11 ) $⋮$ 4          và         56 $⋮$ 4

nên $\left(2.5.4.11-56\right)⋮4$Câu trả lời: Bài 2: