431. Упростите выражение и найдите его значение: 1) 5a · 20b, если a = 4, b = 68; 2) 4m · 50n, если m = 22, n = 34.

### Решение заданий **431.** 1) $5a \cdot 20b = 100ab$. При $a = 4, b = 68$: $100 \cdot 4 \cdot 68 = 400 \cdot 68 = 27200$. 2) $4m \cdot 50n = 200mn$. При $m = 22, n = 34$: $200 \cdot 22 \cdot 34 = 4400 \cdot 34 = 149600$. **432.** 1) $398 \cdot 36 + 36b = 36(398 + b)$. При $b = 602$: $36(398 + 602) = 36 \cdot 1000 = 36000$. 2) $986b - 86 \cdot 83$. Если $b = 83$: $986 \cdot 83 - 86 \cdot 83 = 83(986 - 86) = 83 \cdot 900 = 74700$. **433.** 1) $631 \cdot 18 + x \cdot 369$. При $x = 18$: $18(631 + 369) = 18 \cdot 1000 = 18000$. 2) $58a - 58 \cdot 824$. При $a = 1024$: $58(1024 - 824) = 58 \cdot 200 = 11600$. **434.** 1) $13p + 37p = 50p$. При $p = 14$: $50 \cdot 14 = 700$. 2) $72b - 43b = 29b$. При $b = 54$: $29 \cdot 54 = 1566$. 3) $38x + 17x - 54x + x = (38 + 17 - 54 + 1)x = 2x$. При $x = 678$: $2 \cdot 678 = 1356$. 4) $86c - 35c - c + 296 = 50c + 296$. При $c = 47$: $50 \cdot 47 + 296 = 2350 + 296 = 2646$. **435.** 1) $34x + 66x = 100x$. При $x = 8$: $100 \cdot 8 = 800$. 2) $54a - 39a = 15a$. При $a = 26$: $15 \cdot 26 = 390$. 3) $18m - 5m + 7m = 20m$. При $m = 394$: $20 \cdot 394 = 7880$. 4) $19z - 12z + 33z - 192 = 40z - 192$. При $z = 82$: $40 \cdot 82 - 192 = 3280 - 192 = 3088$.