Toán Lớp 7: Tìm x a) x/4 + 1/7 =25/28 b) 2/5 -3/x= -1/35 c) x +1/9 -1/3 =1/6 d)5/16 -x + 5/11 =-5/6

Question

Toán Lớp 7:  Tìm x a) x/4 + 1/7 =25/28 b) 2/5 -3/x= -1/35 c) x +1/9 -1/3 =1/6 d)5/16 -x + 5/11 =-5/6

tuyetnhungthu · Answer

a)   x/4-1/7=25/28   =>x/4=25/28-1/7   =>x/4=3/4   =>x=3   b)   2/5-3/x-1/35   =>3/x=2/5-(-1/35)   =>3/x=3/7   =>x=7   c)   x+1/9-1/3=1/6   =>x-2/9=1/6   =>x=1/6+2/9   =>x=7/18   d)   5/16-x+5/11=-5/6   =>5/16-x=-5/6-5/11   =>5/16-x=-85/66   =>x=5/16-85/66   =>x=845/528

mocmien87 · Answer

Giải đáp+Lời giải và giải thích chi tiết: a) x/4 + 1/7 =(25)/(28) <=> x/4 = (25)/(28) - 1/7 <=> x/4 = (25)/(28) - 4/(28) <=> x/4 = 3/4 <=> x = 3 Vậy x=3 b) 2/5 - 3/x = -1/(35) <=> 3/x = 2/5 + 1/(35) <=> 3/x = (14)/(35)+1/(35) <=> 3/x = 3/7 <=> 3x = 3.7 <=> 3x=21 <=> x = 7 Vậy x=7 c) x+1/9 - 1/3 = 1/6 <=> x+1/9 = 1/6 + 1/3 <=> x+1/9 = 1/6 + 2/6 <=> x+1/9 = 1/2 <=> x = 1/2-1/9 <=> x = 9/(18)-2/(18) <=> x = 7/(18) Vậy x=7/(18) d) 5/(16)-x+5/(11)=-5/6 <=> 5/(16)-x = (-5)/6 -5/(11) <=> 5/(16)-x = (-55)/(66)-(30)/(66) <=> 5/(16)-x =-(85)/(66) <=> x = 5/(16) + (85)/(66) <=> x= (165)/(528)+(680)/(528) <=> x = (845)/(528) Vậy x = (845)/(528)