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222-9+11+12:2*14+14 = ? ( )

## Toán Lớp 6: Tìm y ∈ Z: a) 7y – 4 = 20 + 3y b) 125 : (3y – 13) = 25 c) 5 x (y – 6) – 2 x (y + 3) = 12 d) 165 – 35 – (35 : y + 3) x 15 = 15 e

Toán Lớp 6: Tìm y ∈ Z:
a) 7y – 4 = 20 + 3y
b) 125 : (3y – 13) = 25
c) 5 x (y – 6) – 2 x (y + 3) = 12
d) 165 – 35 – (35 : y + 3) x 15 = 15
e) (y – 1) x (y + 15) = -9

1. $a)$
$7y – 4 = 20 + 3y$
$7y – 3y = 20 + 4$
$4y = 24$
$y = 6$
$Vậy:$ $y = 6$
$b)$
$125:(3y – 13) = 25$
$3y – 13 = 125 : 25$
$3y – 13 = 5$
$3y = 18$
$y = 6$
$Vậy:$ $y = 6$
$c)$
$5$ xx $(y – 6) – 2$ xx $(y + 3) = 12$
$5y – 30 – 2y – 6 = 12$
$3y – 36 = 12$
$3y = 48$
$y = 16$
$Vậy:$ $y = 16$
$d)$
$165 – 35 – (35 : y + 3)$ xx $15 = 15$
$(35 : y + 3)$ xx $15 = 165 – 35 – 15$
$(35 : y + 3)$ xx $15 = 115$
$35 : y + 3 = \frac{23}{3}$
$35 : y = \frac{14}{3}$
$y = \frac{15}{2}$
$Vậy:$ $y = \frac{15}{2}$
$e)$
$(y – 1)$xx $(y + 15) = -9$
$y(y + 15) – 1(y + 15) = -9$
$y^2 + 15y – y – 15 = -9$
$(y^2 – y) + (15y – 15) = -9$
$y(y – 1) + 15(y – 1) = -9$
$(y – 1)(y + 15) = -9$
$$\left[ \begin{array}{l}y – 1 = -9\\y+15=-9\end{array} \right.$$
$$\left[ \begin{array}{l}y=1\\y=-15\end{array} \right.$$
$Vậy:$ $y = 1$ $hoặc$ $y=-15$
Học tốt.