数学演習/中学校1年生/文字の式/解答のソースを表示

== 文字式の表し方 ==

#&emsp;<math>2a</math>
#&emsp;<math>5ax</math>
#&emsp;<math>-x + y</math>
#&emsp;<math>a^3 b^2</math>
#&emsp;<math>\frac{a}{7}</math>
#&emsp;<math>\frac{x + y}{5}</math>
#&emsp;<math>x + \frac{y}{5}</math>

== 代入と式の値 ==

<math>x= - 3</math>のとき
#&emsp;<math>5x + 7 = 5 \sdot (-3) + 7 = -8</math>
#&emsp;<math>4 - 2x = 4 - 2 \sdot (-3) = 10</math>
#&emsp;<math>- \frac{12}{x} = -\frac{12}{-3} = 4</math>
#&emsp;<math>x^2 = (-3)^2 = 9</math>
#&emsp;<math>-x^2 = -(-3)^2 = -9</math>

== 1次式の加減 ==

#&emsp;<math>5x + 3x = 8x</math>
#&emsp;<math>5a -4a = a</math>
#&emsp;<math>7a + 3 - 5a - 6 = 2a - 3</math>
#&emsp;<math>3x - 2 - x + 9 = 2x + 7</math>
#&emsp;<math>(3a + 2) + (6a - 5) = 3a + 2 + 6a - 5 = 9a - 3</math>
#&emsp;<math>(5x - 9) + (-3x + 9) = 5x - 9 - 3x + 9 = 2x</math>
#&emsp;<math>(5a - 3) - (3a + 2) = 5a - 3 - 3a - 2 = 2a - 5</math>
#&emsp;<math>(a - 7) - (2a + 7) = a - 7 - 2a - 7 = -a - 14</math>

== 1次式と数の乗除 ==

#&emsp;<math>3x \times 4 = 12x</math>
#&emsp;<math>\frac{2}{5} a \times (-10) =  -4a</math>
#&emsp;<math>3(x + 6) = 3x + 18</math>
#&emsp;<math>-4(2x - 5) = -8x + 20</math>
#&emsp;<math>\frac{5a - 3}{7} \times 14 = (5a - 3) \sdot 2 = 10a - 6</math>
#&emsp;<math>12x \div 6 = 2x</math>
#&emsp;<math>9a \div \frac{3}{4} = 9a \sdot \frac{4}{3} = 12a</math>
#&emsp;<math>(18a - 15) \div 3 = 6a - 5</math>
#&emsp;<math>(24a - 8) \div (-8) = -3a + 1</math>
#&emsp;<math>6(a + 2) + 5(2a - 3) = (6a + 12) + (10a - 15) = 16a - 3</math>
#&emsp;<math>2(x + 3) - 3(2x - 1) = (2x + 6) - (6x - 3) 
 = -4x + 9</math>

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