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電子課本網(wǎng) 第78頁(yè)

第78頁(yè)

信息發(fā)布者:
解:根據(jù)題意,得:$\frac{x+1}{3}-\frac{2-x}{2}=1$
去分母,兩邊同時(shí)乘以6,得:$2(x+1)-3(2-x)=6$
去括號(hào),得:$2x + 2 - 6 + 3x = 6$
移項(xiàng),得:$2x + 3x = 6 - 2 + 6$
合并同類項(xiàng),得:$5x = 10$
系數(shù)化為1,得:$x = 2$
∴當(dāng)$x = 2$時(shí),代數(shù)式$\frac{x+1}{3}$的值與代數(shù)式$\frac{2-x}{2}$的值的差為1
解:去分母,得?$5(x-2)-2(x+1)+3=0$?
去括號(hào),得?$5x-10-2x-2+3=0$?
移項(xiàng),得?$5x-2x=10+2-3$?
合并同類項(xiàng),得?$3x=9$?
?$ $?系數(shù)化為?$1,$?得?$x=3$?
解:根據(jù)絕對(duì)值的意義,得:
$\frac{3x - 2}{5} = 3$ 或 $\frac{3x - 2}{5} = -3$
分別解這兩個(gè)方程:
當(dāng) $\frac{3x - 2}{5} = 3$ 時(shí),兩邊同乘5得 $3x - 2 = 15,$移項(xiàng)得 $3x = 17,$解得 $x = \frac{17}{3};$
當(dāng) $\frac{3x - 2}{5} = -3$ 時(shí),兩邊同乘5得 $3x - 2 = -15,$移項(xiàng)得 $3x = -13,$解得 $x = -\frac{13}{3}。$
綜上,方程的解為 $x = \frac{17}{3}$ 或 $x = -\frac{13}{3}。$
解:根據(jù)絕對(duì)值的意義,得:
$2a - 1 = 5 + 7a$ 或 $2a - 1 = -(5 + 7a)$
分別解這兩個(gè)方程:
當(dāng) $2a - 1 = 5 + 7a$ 時(shí),移項(xiàng)得 $2a - 7a = 5 + 1,$合并同類項(xiàng)得 $-5a = 6,$解得 $a = -\frac{6}{5};$
當(dāng) $2a - 1 = -(5 + 7a)$ 時(shí),去括號(hào)得 $2a - 1 = -5 - 7a,$移項(xiàng)得 $2a + 7a = -5 + 1,$合并同類項(xiàng)得 $9a = -4,$解得 $a = -\frac{4}{9}。$
綜上,方程的解為 $a = -\frac{6}{5}$ 或 $a = -\frac{4}{9}。$