Toán Lớp 7: câu 2 a 2/3-(3/4+x)-1/3 b 2/5+3/5x- căn bậc 25/9 làm nhanh giùm mình với

Question

Toán Lớp 7:  câu 2 a 2/3-(3/4+x)-1/3 b 2/5+3/5x- căn bậc 25/9 làm nhanh giùm mình với

daolanhoa · Answer

a) 2/3-(3/4+x)=1/3 <=>3/4-x=2/3-1/3 <=>3/4-x=1/3 <=>x=1/3-3/4 <=>x=-5/12 Vậy x=-5/12 b)2/5+3/5x=$ sqrt{ dfrac{25}{9} }$ <=>2/5+3/5x=±5/3 <=> ( left[ begin{array}{l} dfrac{2}{5} + dfrac{3}{5}x= dfrac{5}{3} dfrac{2}{5} + dfrac{3}{5}x=- dfrac{5}{3} end{array} right. ) <=> ( left[ begin{array}{l} dfrac{3}{5}x= dfrac{5}{3}- dfrac{2}{5} dfrac{3}{5}x=- dfrac{5}{3}- dfrac{2}{5} end{array} right. ) <=> ( left[ begin{array}{l} dfrac{3}{5}x= dfrac{19}{5} dfrac{3}{5}x=- dfrac{31}{15} end{array} right. ) <=> ( left[ begin{array}{l} x= dfrac{19}{5}: dfrac{3}{5} x=- dfrac{31}{15}: dfrac{3}{5} end{array} right. ) <=> ( left[ begin{array}{l} x= dfrac{19}{19} x=- dfrac{31}{9} end{array} right. ) Vậy x ∈{19/9;- 31/9} @thew

phuongthuydung · Answer

a,   2/3 - ( 3/4 + x ) = 1/3   3/4 + x = 2/3 - 1/3   3/4 + x = 1/3   x = 1/3 - 3/4   x = -5/12   => x = -5/12   b,   2/5 + 3/5x =  $ sqrt{ dfrac{25}{9}}$   2/5 + 3/5x = &plusmn;5/3   - TH1: 2/5 + 3/5x = 5/3   3/5x = 5/3 - 2/5   3/5x = 19/15   x = 19/15 : 3/5   x = 19/9   - TH2: 2/5 + 3/5x = -5/3   3/5x = -5/3 - 2/5   3/5x = -31/15   x = -31/15 : 3/5   x = -31/9   => x &isin; { 19/9; -31/9 }