в) г)
782 − 302 662 − 62 1012 − 312 1392 − 292
( 78 − 30 )( 78 + 30 ) = 48 ⋅ 108 = 4 ⋅ 108 = 108 = 6 = 1 1 ; ( 66 − 6 )( 66 + 6 ) 60 ⋅ 72 5 ⋅ 72 5 ⋅ 18 5 5 (101 − 31)(101 + 31) = 70 ⋅ 132 = 7 ⋅ 132 = 7 ⋅ 12 = 1 = (139 − 29 )(139 + 29 ) 110 ⋅ 168 11 ⋅ 168 168 2
=
№ 551
а) б) в) г)
7,8 ⋅ 8,7 + 7,8 ⋅ 1,3 7,8 ( 8,7 + 1,3) 7,8 ⋅ 10 = = = 0,78; 100 100 100 13, 2 ⋅ 9,8 + 13, 2 ⋅ 2, 2 13, 2 ( 9,8 + 2, 2 ) 13, 2 ⋅ 12 = 6,6; = = 24 24 24 2,6 ⋅ 5, 4 + 5, 4 ⋅ 0,6 5, 4 ( 2,6 + 0,6 ) 5, 4 ⋅ 3, 2 = = = 1,6; 10,8 10,8 10,8 4,5 ⋅ 3,1 + 4,5 ⋅ 2,1 4,5 ( 3,1 + 2,1) 4,5 ⋅ 5, 2 = = = 4,5 · 52 = 234. 0,1 0,1 0,1
§ 20. Вынесение общего множителя за скобки № 552 а) 1, 2, 2m; б) x, 2x, 4x; в) a, b, ab; г) z, 2z, 7z. № 553 а) (3x + 3y) = 3(x + y); б) (5a – 5b) = 5(a – b); в) 7a + 7y = 7(a + y); г) 8x – 8a = 8(x – a). № 554 а) 3x + 6y = 3(x + 2y); б) 5a – 15b = 5(a – 3b); г) 8x – 32a = 8(x – 4a). в) 7a + 14y = 7(a + 2y); № 555 а) 8x + 28y = 4(x + 3y); б) 15a – 25 b = 5(3a – 5b); в) 21a + 28y = 7(3a + 4y); г) 24x – 32a = 8(3x – 4a). № 556 а) 2,4x + 7,2y = 2,4(x + 3y); б) 1,8a – 2,4b = 0,6(3a – 4b); в) 0,01a + 0,03y = 0,01(a + 3y); г) 1,25x – 1,75a =0,25(5x – 7a). № 557 1 4 1 8 16 8 2 а) x + y = (x + 4y); б) a – b = (a – b); 3 3 3 9 27 9 3 в)
18 12 a+ y= 25 35
6⎛3 2 ⎞ ⎜ a + y⎟ ; 5⎝5 7 ⎠
г)
3⎛ 4 1 ⎞ 12 3 x– y = ⎜ x − y⎟ . 7⎝7 4 ⎠ 49 28
№ 558 1 5
2 5
а) 3 x + 3 y = 90
16 17 1 x + y = (16x + 17y); 5 5 5