Toán Lớp 7: bai 1 a) x+1/3=2/5-(-1/3) b) Ix-1,5I-2=0 c) (1/2)^x+1-1/2=3/8

Question

Toán Lớp 7:  bai 1  a) x+1/3=2/5-(-1/3) b) Ix-1,5I-2=0 c) (1/2)^x+1-1/2=3/8

diemchau · Answer

Giải đáp:   a)   x+1/3=2/5-(-1/3)   &rArr;x+1/3=2/5+1/3   &rArr;x=2/5+1/3-1/3   &rArr;x=2/5   Vậy x=2/5   b)   |x-1,5|-2=0   &rArr;|x-1,5|=2   $&rArr; left[ begin{matrix}x-1,5=2   x-1,5=-2 end{matrix} right.$   $&rArr; left[ begin{matrix}x=3,5   x=-0,5 end{matrix} right.$   Vậy x&isin;{3,5;-0,5}   c) *Sửa đề.    (1/2)^(x+1)-1/2=-3/8   &rArr;(1/2)^(x+1)=-3/8+1/2   &rArr;(1/2)^(x+1)=1/8   &rArr;(1/2)^(x+1)=(1/2)^3   &rArr;x+1=3   &rArr;x=2   Vậy x=2

kimlien · Answer

*Giải đáp + giải th&iacute;ch c&aacute;c bước giải :     a) x+1/3=2/5-(-1/3)   =>x+1/3=2/5+1/3   =>x+1/3=11/15   =>x=11/15-1/3   =>x=2/5   Vậy x=2/5    ----------------------------   b) |x-1,5|-2=0   =>|x-1,5| =0+2   =>|x-1,5|=2   => ( left[  begin{array}{l}x-1,5=2  x-1,5=-2 end{array}  right. )$  $=> ( left[  begin{array}{l}x=2+1,5  x=-2+1,5 end{array}  right. )$  $=> ( left[  begin{array}{l}x=3,5  x=-0,5 end{array}  right. )   Vậy x  in {3,5;-0,5}   --------------------------------   c) Đề sai n&ecirc;n mk sửa nh&eacute; :   (1/2)^(x+1) - 1/2=-3/8   =>(1/2)^(x+1)=-3/8+1/2   =>(1/2)^(x+1)=1/8   =>(1/2)^(x+1)=(1/2)^3   =>x+1=3   =>x=3-1   =>x=2   Vậy x=2   -----------------------------------------------   #Blue