Toán Lớp 8: a,3x-2(x+5)-3=4-3(2x-1)
b,5(2x-3)-4(5x-7)=19-2(x+11)
c,4(x+3)-7x+17=8(5x-1)+166 d,17-14(x+1)=13-4(x+1)-x(5-3)
e,7(4x+3)-x(4-1)=15(x+0,75)+7 giải phương trình bậc nhất
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Giải đáp + Lời giải và giải thích chi tiết:
a) $3x – 2(x + 5) – 3 = 4-3(2x – 1)$
$\Leftrightarrow 3x – 2x – 10 – 3 = 4 – 6x + 3$
$\Leftrightarrow x – 13 = -6x + 7$
$\Leftrightarrow x + 6x = 13 + 7$
$\Leftrightarrow 7x = 20$
$\Leftrightarrow x = \dfrac{20}{7}$
b) $5(2x – 3) – 4(5x – 7) = 19 – 2(x + 11)$
$\Leftrightarrow 10x – 15 – 20x + 28 = 19 – 2x – 22$
$\Leftrightarrow -10x + 13 = -2x – 3$
$\Leftrightarrow -10x + 2x = -13 – 3$
$\Leftrightarrow -8x = -16$
$\Leftrightarrow x = \dfrac{-16}{-8} = 2$
c) $4(x + 3) – 7x + 17 = 8(5x – 1) + 166$
$\Leftrightarrow 4x + 12 – 7x + 17 = 40x – 8 + 166$
$\Leftrightarrow -3x + 29 = 40x + 158$
$\Leftrightarrow -3x – 40x = -29 + 158$
$\Leftrightarrow -43x = 129$
$\Leftrightarrow x = \dfrac{129}{-43} = -3$
d) $17 – 14(x + 1) = 13-4(x + 1) – x(5-3)$
$\Leftrightarrow 17 – 14x – 14 = 13 – 4x – 4 – 2x$
$\Leftrightarrow -14x + 3 = -6x + 9$
$\Leftrightarrow -14x + 6x = -3 + 9$
$\Leftrightarrow -8x = 6$
$\Leftrightarrow x = \dfrac{6}{-8} = \dfrac{-3}{4}$
e) $7(4x + 3) – x(4 – 1) = 15(x + 0,75) + 7$
$\Leftrightarrow 28x + 21 – 3x = 15x – 11,25 + 7$
$\Leftrightarrow 25x + 21 = 15x – 4,25$
$\Leftrightarrow 25x – 15x = -21 – 4,25$
$\Leftrightarrow 10x = -25,25$
$\Leftrightarrow x = \dfrac{-25,25}{10} = -2,525$
Giải đáp+Lời giải và giải thích chi tiết:
a) 3x-2(x+5)-3=4-3(2x-1)
<=>3x-2x-10-3=4-6x+3
<=>x-13=-6x+7
<=>x+6x=7+13
<=>7x=20
<=>x=20/7
Vậy S={20/7}
b) 5(2x-3)-4(5x-7)=19-2(x+11)
<=>10x-15-20x+28=19-2x-22
<=>-10x+13=-2x-3
<=>-2x+10x=13+3
<=>8x=16
<=>x=2
Vậy S={2}
c) 4(x+3)-7x+17=8(5x-1)+166
<=>4x+12-7x+17=40x-8+166
<=>-3x+29=40x+158
<=>40x+3x=29-158
<=>43x=-129
<=>x=-3
Vậy S={-3}
d) 17-14(x+1)=13-4(x+1)-x(5-3)
<=>17-14x-14=13-4x-4-2x
<=>-14x+3=-6x+9
<=>-6x+14x=3-9
<=>8x=-6
<=>x=-3/4
Vậy S={-3/4}
e) 7(4x+3)-x(4-1)=15(x+0,75)+7
<=>28x+21-3x=15x+11,25+7
<=>25x+21=15x+18,25
<=>25x-15x=18,25-21
<=>10x=-11/4
<=>x=-11/40
Vậy S={-11/40}