$a=3$、 $b=-2$のとき、次の9つの式の値を求めます。 (1) $4a+7b$ (2) $5a+4b$ (3) $2a-5b$ (4) $3a+2b+a+5b$ (5) $2a+5b+3a-b$ (6) $4a+b+3b+a$ (7) $7a+9b-2a-5b$ (8) $5a-7b-3a+2b$ (9) $6a-2b-4a-3b$

1. 問題の内容

$a=3$、 $b=-2$のとき、次の9つの式の値を求めます。

(1) $4a+7b$

(2) $5a+4b$

(3) $2a-5b$

(4) $3a+2b+a+5b$

(5) $2a+5b+3a-b$

(6) $4a+b+3b+a$

(7) $7a+9b-2a-5b$

(8) $5a-7b-3a+2b$

(9) $6a-2b-4a-3b$

2. 解き方の手順

各式に $a=3$、 $b=-2$を代入して計算します。

(1) $4a+7b = 4(3) + 7(-2) = 12 - 14 = -2$

(2) $5a+4b = 5(3) + 4(-2) = 15 - 8 = 7$

(3) $2a-5b = 2(3) - 5(-2) = 6 + 10 = 16$

(4) $3a+2b+a+5b = 4a + 7b = 4(3) + 7(-2) = 12 - 14 = -2$

(5) $2a+5b+3a-b = 5a + 4b = 5(3) + 4(-2) = 15 - 8 = 7$

(6) $4a+b+3b+a = 5a + 4b = 5(3) + 4(-2) = 15 - 8 = 7$

(7) $7a+9b-2a-5b = 5a + 4b = 5(3) + 4(-2) = 15 - 8 = 7$

(8) $5a-7b-3a+2b = 2a - 5b = 2(3) - 5(-2) = 6 + 10 = 16$

(9) $6a-2b-4a-3b = 2a - 5b = 2(3) - 5(-2) = 6 + 10 = 16$

3. 最終的な答え

(1) -2

(2) 7

(3) 16

(4) -2

(5) 7

(6) 7

(7) 7

(8) 16

(9) 16