The seventh grade mathematics textbook answer (1) exercise 59 pages.
1. Solution: (1) 6a? cm？ ; (2)80% one yuan; (3)ut km； (4)[(a+x)b-ab]m？ .
2. Solution: (1) (t+5)℃; (2)3(x-y) kilometers or (3x-3y) kilometers; (3) (50-5x) yuan. (4) (? r？ A-? r？ a) cm3。
3.
4. Solution: (1) The number of years per year increases, and the height of the tree increases by 5 cm; (2) (100+5n) cm.
5. Solution: The second row has (a+ 1) seats; There are (a+2) seats in the third row; The number of seats in N rows is (a+n-1); 20+ 19- 1=38 (pieces).
6. Solution: V=( 1/2a? -? r？ )h( cm？ ). when a=6cm, r=0.5cm, h=0.2 cm, v? ( 1/2? 6? -3? 0.5? )? 0.2=3.45 (cm? ).
7. Solution: (1) 2n; (2)2n+ 1 (or 2n- 1).
8. Solution: Compared with the three teams, the total matching number is (3 (3-1))/2 = 3; Four teams, the total number of games is (4 (4-1))/2 = 6;
Five teams compete. The total number of matches is (5 (5-1))/2 =10;
N teams, the total number of games is (n(n- 1))/2.
9. solution: password L dp d jluo, deciphered? Keys? x-3。
What does the password mean? I am a girl? .
(The answer is not unique, but reasonable)
The seventh grade mathematics textbook answers (2) exercises 67 pages.
1. Solution: (1)12 (x-0.5) =12x-6.
(2)-5( 1- 1/5x)=-5+x = x-5。
(3)-5a+(3a-2)-(3a-7)=-5a+3a-2-3a+7 =-5a+5。
(4) 1/3(9y-3)+2(y+ 1)= 3y- 1+2y+2-5y+ 1。
2. Solution: The 4-hour journey of the plane flying downwind is 4 (A+20) km; 3(a-20)km is the distance that the plane flies against the wind for 3 hours; The difference between the two trips is 4 (a+20)-3 (a-20) = 4a+80-3a+60 = (a+140) (km).
The seventh grade mathematics textbook answers (3) exercises 69 pages.
1. Solution: (1) 3xy-4xy-(-2xy) = 3xy-4xy+2xy = xy.
(2)- 1/3ab- 1/4a？ + 1/3a？ -(-2/3ab)=(- 1/3+2/3)a b+(- 1/4+ 1/3)a？ = 1/3ab+ 1/ 12a？ .
2.( 1)6x？ -7x+2。 (2)7a？ -3ab。
3. Solution: 5(3a? b-ab？ )- (ab？ +3a？ b)= 15a？ b-5ab？ -ab？ -3a？ b= 12a？ b-6ab？ .