Câu 25: Tìm số nguyên x biết:
a) -5.(-x + 7) – 3.(-x – 5) = -4.(12 – x ) + 48 c) 7.(-x – 7) – 5.(-x – 3) = 12.(3 – x)
b) -2.(15 – 3x) – 4.(-7x + 8) = -5 – 9.(-2x + 1) d) 5.(-3x – 7) – 4.(-2x – 11) = 7.(4x + 10) + 9
Câu 25: Tìm số nguyên x biết:
a) -5.(-x + 7) – 3.(-x – 5) = -4.(12 – x ) + 48 c) 7.(-x – 7) – 5.(-x – 3) = 12.(3 – x)
b) -2.(15 – 3x) – 4.(-7x + 8) = -5 – 9.(-2x + 1) d) 5.(-3x – 7) – 4.(-2x – 11) = 7.(4x + 10) + 9
Bạn tham khảo:
$a) -5.(-x + 7) – 3.(-x – 5) = -4.(12 – x ) + 48$
$⇔ -5x – 35 + 3x + 15 = -48 +4x + 48$
$⇔ -5x + 3x – 4x = -48 + 48 – 15 + 35$
$⇔ -2x = 20$
$⇔ x = -10$
$c) 7.(-x – 7) – 5.(-x – 3) = 12.(3 – x)$
$⇔ -7x -49 + 5x + 15 = 36 – 12x$
$⇔ -7x + 5x + 12x = 36 – 15 + 49$
$⇔ 10x = 70$
$⇔ x = 7$
$b) -2.(15 – 3x) – 4.(-7x + 8) = -5 – 9.(-2x + 1)$
$⇔ -30 + 6x + 28x – 32 = -5 + 18x – 9$
$⇔ 6x + 28x – 18x = -5 -9+30+32$
$⇔ 16x = 48$
$⇔ x = 3$
$d) 5.(-3x – 7) – 4.(-2x – 11) = 7.(4x + 10) + 9$
$⇔ -15x – 35 + 8x + 44 = 28x + 70 + 9$
$⇔ -15x + 8x – 28x = 70 + 9 – 44 + 35$
$⇔ -35x = 70$
$⇔ x = -2$
Đáp án:
Giải thích các bước giải: