Đáp án+Giải thích các bước giải:
Bài 1:
a) 3 . 5^2 - 64 : 2^3
= 3 . 25 - 64 : 8
= 75 - 8
= 67
b) 250 - [49 - (15 - 11)^2]
= 250 - (49 - 4^2)
= 250 - (49 - 4^2)
= 250 - (49 - 16)
= 250 - 33
= 217
c) [213 - (90 + 2^2 + 3^2)] : 11 + 32
= [213 - (90 + 4 + 9)] : 11 + 32
= (213 - 103) : 11 + 32
= 110 : 11 + 32
= 10 + 32 = 42
d, {38 + [63 - 24 : 6 + (5 - 2)^2] : 4} . 2
= {38 + [63 - 4 + 3^2] : 4} . 2
= [ 38 + (63 - 4 + 9) : 4] . 2
= (38 + 68 : 4) . 2
= (38 + 17) . 2
Bài 2 :
a)
$720:(41-x)=2^3.5\\\ 720:(41-x)=40\\\ 41-x=18\\\ x=23$
b)
$2x+5x=343\\\ x.(2+5)=343\\\ x.7=343\\\ x=49$
c)
$3^x=3^2. 27\\\ 3^x=3^2. 3^3\\\ 3^x=3^5\\\ x=5$
d)
$2^x+2^{x+4}=272\\\ 2^x.(1+2^4)=272\\\ 2^x.17=272\\\ 2^x=16\\\ 2^x=2^4\\\ x=4$
Bài 3 :
