Bài 4 1, 55 – 5(x + 3) = 8 2, 175 – 5(x + 3) = 85 3, 4x – 40 = |-4| + 12 4, x + 15 = 20 – 4x 5, 8x + |-3| = -4x + 39 6, 6(x – 2) + (-2) = 20 – 4x Bài

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1. Bài 4: 

   1, $55 – 5(x + 3) = 8$

   $⇔  55 – 5x – 15 = 8$

   $⇔ 70 – 5x = 8$

   $⇔ 5x = 62$

   $⇔ x = 62 : 5$

   $⇔ x = \frac {62}{5} = 12,4$

   2, $175 – 5(x + 3) = 85$

   $⇔  175 – 5x – 15 = 85$

   $⇔ 160 – 5x = 85$

   $⇔ 5x = 75$

   $⇔ x = 75 : 5$

   $⇔ x = 15$

   3, $4x – 40 = |-4| + 12$

   $⇔ 4x – 40 = 4 + 12$

   $⇔ 4x – 40 = 16$

   $⇔ 4x = 56$

   $⇔ x = 56 : 4$

   $⇔ x = 14$

   4, $x + 15 = 20 – 4x$

   $⇔ x + 4x = 20 – 15$

   $⇔ 5x = 5$

   $⇔ x = 5 : 5$

   $⇔ x = 1$

   5, $8x + |-3| = -4x + 39$

   $⇔ 8x + 3 = -4x + 39$

   $⇔ 8x + 4x = 39 – 3$

   $⇔ 8x + 4x = 36$

   $⇔ 12x = 36$

   $⇔ x = 36 : 12$

   $⇔ x = 3$

   6, $6(x – 2) + (-2) = 20 – 4x$

   $⇔6x – 12 + (-2) = 20 – 4x$

   $⇔ 6x – 14 = 20 – 4x$

   $⇔ 6x + 4x = 20 + 14$

   $⇔ 10x = 34$

   $⇔ x = 34 : 10$

   $⇔ x = \frac {17}{5} = 3,4$

   Bài 5: 

   a. $2(x – 5) – 3(x + 7) = 14$

   $⇔ 2x – 10 – 3x – 21 = 14$

   $⇔ -x – 31 = 14$

   $⇔ x = -31 – 14$

   $⇔ x = -45$

   b. $5(x – 6) – 2(x + 3) = 12$

   $⇔ 5x – 30 – 2x – 6 = 12$

   $⇔ 3x – 36 = 12$

   $⇔ 3x = 48$

   $⇔ x = 48 : 3$

   $⇔ x = 16$

   c. $3(x – 4) – (8 – x) = 12$

   $⇔ 3x – 12 – 8 + x = 12$

   $⇔ 4x – 20 = 12$

   $⇔ 4x = 32$

   $⇔ x = 32 : 4$

   $⇔ x = 8$

   d. $-7(3x – 5) + 2(7x – 14) = 28$

   $⇔ -21x + 35 + 14x – 28 = 28$

   $⇔ -7x – 7 = 28$

   $⇔ -7x = 21$

   $⇔ x = 21 : (-7)$

   $⇔ x = -3$

   e. $5(3 – 2x) + 5(x – 4) = 6 – 4x$

   $⇔ 15 – 10x + 5x – 20 = 6 – 4x$

   $⇔ -x – 11 = 0$

   $⇔ x = -11$

   f. $-5(2 – x) + 4(x – 3) = 10x – 15$

   $⇔ -10 + 5x + 4x -12 = 10x – 15$

   $⇔ -x = 7$

   $⇔ x = -7$

   g. $2(4x – 8) – 7(3 + x) = |-4|(3 – 2)$

   $⇔ 8x – 16 – 21 – 7x = 4.1$

   $⇔ x = 4 + 21 + 16$

   $⇔ x = 41$

   h. $8(x – |-7|) – 6(x – 2) = |-8|.6 – 50$

   $⇔ 8(x – 7) – 6x + 12 = 8.6 – 50$

   $⇔ 8x – 56 – 6x + 12 = 48 – 50$

   $⇔ 2x = -2 – 12 + 56$

   $⇔ 2x = 46$

   $⇔ x = 46 : 2$

   $⇔ x = 23$

   k. $-7(5 – x) – 2(x – 10) = 15$

   $⇔ -35 + 7x – 2x + 20 = 15$

   $⇔ 5x = 15 – 20 + 35$

   $⇔ 5x = 30$

   $⇔ x = 30 : 5$

   $⇔ x = 6$

   l. $4(x – 1) – 3(x – 2) = -|-5|$

   $⇔ 4x – 4 – 3x + 6 = -5$

   $⇔ x = -5 + 4 – 6$

   $⇔ x = -7$

   m. $-4(x + 1) + 89(x – 3) = 24$

   $⇔ -4x – 4 + 89x – 276 = 24$

   $⇔ 85x = 295$

   $⇔ x = 295 : 85$

   $⇔ x = \frac {259}{85} = \frac {59}{17} = 3,5$

   n. $5(x – 30) – 2(x + 6) = 9$

   $⇔ 5x – 150 – 2x – 12 = 9$

   $⇔ 3x = 171$

   $⇔ x = 171 : 3$

   $⇔ x = 57$

   o. $-3(x – 5) + 6(x + 2) = 9$

   $⇔ -3x + 15 + 6x + 12 = 9$

   $⇔ 3x = -18$

   $⇔ x = -18 : 3$

   $⇔ x = -6$

   p. $7(x – 9) – 5(6 – x) = – 6 + 11x$

   $⇔ 7x – 63 – 30 + 5x = -6 + 11x$

   $⇔ 12x = 98$

   $⇔ x = 98 : 12$

   $⇔ x = \frac {49}{6} = 4,2$

   q. $10(x – 7) – 8(x + 5) = 6.(-5) + 24$

   $⇔ 10x – 70 – 8x – 40 = -30 + 24$

   $⇔ 2x = 104$

   $⇔ x = 104 : 2$

   $⇔x = 52$ 

    

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