Toán Lớp 8: Giải các phương trình
a) 7 + 2x = 22 – 3x
b) 8x – 3 = 5x+12
c) x – 12+ 4x = 25+ 2x-1
d) x + 2x + 3x – 19 = 3x +5
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Toán Lớp 8: Giải các phương trình
a) 7 + 2x = 22 – 3x
b) 8x – 3 = 5x+12
c) x – 12+ 4x = 25+ 2x-1
d) x + 2x + 3x – 19 = 3x +5
Comments ( 2 )
a. 7 + 2x = 22 – 3x
<=> 2x + 3x = 22 – 7
<=> 5x = 15
<=> x = 3
b. 8x – 3 = 5x + 12
<=> 8x – 5x = 12 + 3
<=> 3x = 15
<=> x = 5
c. x – 12 + 4x = 25 + 2x – 1
<=> x – 2x + 4x = 25 – 1 + 12
<=> 3x = 36
<=> x = 12
d. x + 2x + 3x – 19 = 3x + 5
<=> x + 2x + 3x – 3x = 5 + 19
<=> 3x = 24
<=> x = 8
Chúc bạn học tốt nha !!!
$a)$ $7+2x=22−3x\:$
$⇔7+2x-7=22-3x-7$
$⇔2x=-3x+15$
$⇔2x+3x=-3x+15+3x$
$⇔5x=15$
$⇔x=3$
$\text{Vậy pt có nghiệm S = {3}}$
___________________________
$b)$ $8x-3=5x+12$
$⇔8x-3+3=5x+12+3$
$⇔8x=5x+15$
$⇔8x-5x=5x+15-5x$
$⇔3x=15$
$⇔x=5$
$\text{Vậy pt có nghiệm S = {5}}$
___________________________
$c)$ $x−12+4x=25+2x−1\:\:$
$⇔x+4x-12=25+2x-1$
$⇔5x-12=25+2x-1$
$⇔5x-12=2x+25-1$
$⇔x-12+12=2x+24+12$
$⇔5x=2x+36$
$⇔5x-2x=2x+36-2x$
$⇔3x=36$
$⇔x=12$
$\text{Vậy pt có nghiệm S = {12}}$
___________________________
$d)$ $x+2x+3x-19=3x+5$
$⇔x+2x+3x-19-3x=3x+5-3x$
$⇔x+2x-19=5$
$⇔3x-19=5$
$⇔3x-19+19=5+19$
$⇔3x=24$
$⇔x=8$
$\text{Vậy pt có nghiệm S = {8}}$