Toán Lớp 7: a) x+1/10 + x+1/11 + x+1/12 = x+1/13 + x+1/14 b) 3/2-4(1/4-x)=2/3-7x c)(x-2/7).(x+5/4)=0 d)2/3-5/3x=7/10x+5/6

Question

Toán Lớp 7:  a) x+1/10 + x+1/11 + x+1/12 = x+1/13 + x+1/14 b) 3/2-4(1/4-x)=2/3-7x c)(x-2/7).(x+5/4)=0 d)2/3-5/3x=7/10x+5/6

baoquyen · Answer

Giải đáp + Lời giải và giải thích chi tiết:     a)   (x+1)/(10)+(x+1)/(11)+(x+1)/(12)=(x+1)/(13)+(x+1)/(14)   ->(x+1)/(10)+(x+1)/(11)+(x+1)/(12)-(x+1)/(13)-(x+1)/(14)=0   ->(x+1)((1)/(10)+(1)/(11)+(1)/(12)-(1)/(13)-(1)/(14))=0   ->x+1=0 . V&igrave; (1)/(10)+(1)/(11)+(1)/(12)-(1)/(13)-(1)/(14) ne0   ->x=-1   b)   (3)/(2)-4((1)/(4)-x)=(2)/(3)-7x   ->(3)/(2)-1+4x=(2)/(3)-7x   ->(1)/(2)+4x=(2)/(3)-7x   ->4x+7x=(2)/(3)-(1)/(2)   ->11x=(1)/(6)   ->x=(1)/(66)   c)   (x-(2)/(7))(x+(5)/(4))=0   ->  ( left[  begin{array}{l}x- dfrac{2}{7}=0  x+ dfrac{5}{4}=0 end{array}  right. )    ->  ( left[  begin{array}{l}x= dfrac{2}{7}  x=- dfrac{5}{4} end{array}  right. )    d)   (2)/(3)-(5)/(3)x=(7)/(10)x+(5)/(6)   ->(7)/(10)x+(5)/(3)x=(2)/(3)-(5)/(6)   ->(71)/(30)x=-(1)/(6)   ->x=-(5)/(71)

tuyetanhthu · Answer

Giải đáp + Lời giải và giải thích chi tiết: a) (x+1)/10+(x+1)/11+(x+1)/12=(x+1)/13+(x+1)/14 <=>(x+1)/10+(x+1)/11+(x+1)/12-(x+1)/13-(x+1)/14=0 <=>(x+1)(1/10+1/11+1/12-1/13-1/14)=0 <=>x+1=0<=>x=-1 (Vì 1/10+1/11+1/12-1/13-1/14ne0) Vậy x= -1 b) 3/2-4(1/4-x)=2/3-7x <=>3/2-1+4x-2/3+7x=0 <=>(3/2-1-2/3)+(4x+7x)=0 <=>-1/6+11x=0 <=>-1/6=-11x <=>x=(-1/6):(-11) <=>x=1/66 Vậy x = 1/66 c) (x-2/7)(x+5/4)=0 TH1 : x-2/7=0<=>x=2/7 TH2 : x+5/4=0<=>x=-5/4 Vậy x in {2/7;-5/4} d) 2/3-5/3x=7/10x+5/6 <=>2/3-5/6=7/10x+5/3x <=>-1/6=71/30x <=>x=(-1/6):71/30 <=>x=(-1/6)*30/71 <=>x=(-1/1)*5/71 <=>x=-5/71 Vậy x = -5/71.