Toán Lớp 6: a,(3x-2^4).7^3=2.7^4 b,720:[41-(2x-5)]=2^2.5 c,[230-(15-5x)].3=390

Question

Toán Lớp 6:  a,(3x-2^4).7^3=2.7^4 b,720:[41-(2x-5)]=2^2.5 c,[230-(15-5x)].3=390

mocmien87 · Answer

a, ( 3x - $2^{4}$ ) . 7&sup3; = 2. $7^{4}$           3x - 16                   = 2. $7^{4}$ : 7&sup3;        3x - 16                   = 14             3x                       = 14 + 16              3x                      = 30               x                      = 30 : 3              x                       = 10      b, 720 : [41 - ( 2x-5 ) ] = 2&sup2; . 5           720 : [41 - ( 2x-5 ) ] = 4 . 5        720 : [41 - ( 2x-5 ) ] = 20                  41 - ( 2x-5 )   = 720 : 20                  41 - ( 2x-5 )   = 36                          2x-5      = 41 - 36                          2x-5       = 5                          2x          = 5+5                         2x          = 10                           x          = 10 : 2                           x          = 5      c,    [ 230 - (15-5x ) ] . 3 = 390              230 - (15-5x )        = 390 : 3           230 - (15-5x )        = 130                      15-5x           = 230 - 130                      15-5x           = 100                           5x           = 15 - 100                          5x           = -85                           x            = -85 : 5                           x            = -17

thanhmaianh · Answer

Lời giải chi tiết:     a) (3x-2^4).7^3=2.7^4   =>3x-2^4=2.7^4:7^3   =>3x-16=2.7   =>3x-16=14   =>3x=14+16   =>3x=30   =>x=30:3   =>x=10   Vậy x=10   b) 720:[41-(2x-5)]=2^(2).5   =>720:[41-(2x-5)]=20   =>41-(2x-5)=720:20   =>41-(2x-5)=36   =>2x-5=41-36   =>2x-5=5   =>2x=5+5   =>2x=10   =>x=10:2   =>x=5   Vậy x=5   c) [230-(15-5x)].3=390   =>230-(15-5x)=390:3   =>230-(15-5x)=130   =>15-5x=230-130   =>15-5x=100   =>5x=100+15   =>5x=115   =>x=115:5   =>x=23   Vậy x=23