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# 数学演習/中学校1年生/文字の式

## 文字式の表し方

1. ${\displaystyle 2\times a}$
2. ${\displaystyle a\times x\times 5}$
3. ${\displaystyle x\times (-1)+y\times 1}$
4. ${\displaystyle a\times b\times a\times a\times b}$
5. ${\displaystyle a\div 7}$
6. ${\displaystyle (x+y)\div 5}$
7. ${\displaystyle x+y\div 5}$

## 代入と式の値

${\displaystyle x=-3}$のとき、次の式の値を求めなさい。

1. ${\displaystyle 5x+7}$
2. ${\displaystyle 4-2x}$
3. ${\displaystyle -{\frac {12}{x}}}$
4. ${\displaystyle x^{2}}$
5. ${\displaystyle -x^{2}}$

## 1次式の加減

1. ${\displaystyle 5x+3x}$
2. ${\displaystyle 5a-4a}$
3. ${\displaystyle 7a+3-5a-6}$
4. ${\displaystyle 3x-2-x+9}$
5. ${\displaystyle (3a+2)+(6a-5)}$
6. ${\displaystyle (5x-9)+(-3x+9)}$
7. ${\displaystyle (5a-3)-(3a+2)}$
8. ${\displaystyle (a-7)-(2a+7)}$

## 1次式と数の乗除

1. ${\displaystyle 3x\times 4}$
2. ${\displaystyle {\frac {2}{5}}a\times (-10)}$
3. ${\displaystyle 3(x+6)}$
4. ${\displaystyle -4(2x-5)}$
5. ${\displaystyle {\frac {5a-3}{7}}\times 14}$
6. ${\displaystyle 12x\div 6}$
7. ${\displaystyle 9a\div {\frac {3}{4}}}$
8. ${\displaystyle (18a-15)\div 3}$
9. ${\displaystyle (24a-8)\div (-8)}$
10. ${\displaystyle 6(a+2)+5(2a-3)}$
11. ${\displaystyle 2(x+3)-3(2x-1)}$