Đáp án + Giải thích các bước giải:
Bài 1 ;
a) $\frac{1}{10}$ - $\frac{1}{2}$+ $\frac{7}{5}$
= $\frac{1}{10}$ - $\frac{5}{10}$ + $\frac{14}{10}$
= 1
c) 7 $\frac{5}{9}$ - ( 2 $\frac{5}{9}$ - 1 $\frac{4}{7}$ )
= ( 7 $\frac{5}{9}$ - 2 $\frac{5}{9}$ ) + 1 $\frac{4}{7}$
= 5 + 1 $\frac{4}{7}$
= 6 $\frac{4}{7}$
Bai 2 :
a) 60% x - x + $\frac{1}{3}$ = 2
$\frac{3}{5}$ x - x = 2 - $\frac{1}{3}$
$\frac{3}{5}$ x - x = $\frac{5}{3}$
$\frac{3}{5}$ x = $\frac{5}{3}$+ x
đến đây bạn tự suy nghĩ nha , mình chịu
d) $\frac{2x}{3.5}$ + $\frac{2x}{5.7}$ + ... + $\frac{2x}{97.99}$ = 1
$\frac{2x}{3}$ + $\frac{2x}{5}$ - $\frac{2}{5}$ + $\frac{2x}{7}$ + ... + $\frac{2x}{97}$ - $\frac{2x}{99}$ = 1
$\frac{2x}{3}$ - $\frac{2x}{99}$ = 1
$\frac{(2x).33}{99}$ - $\frac{2x}{99}$ = $\frac{99}{99}$
2x .33 - 2x = 99
2x . 33 - 2x . 1 = 99
2x . ( 33 - 1 ) = 99
2x . 32 = 99
2x = 99 : 32
2x = $\frac{99}{32}$
x = $\frac{99}{32}$ : 2
x = $\frac{99}{64}$
