七年级下册数学书答案，苏科版七年级下册数学( 八 ) _同旁内角

① into ③ to get -x+2(5-x-3z) +z=2,
to -3x-5z=-8. ④
z=2 into ④, get -3x-5×2=-8,
x=-2/3,
x=-2/3, z=2 into ②,
Get a 2/3+y+2=1, theis y=1/3.
④⑤ to get aof
④×2-⑤, 15z=15, z=1.
z=1 into ⑤ to get x=-1.
x=-1, z=1 into ①, get y=-2.
①+③, 5y=10, ie y=2.
y=2 into ④ to get x=1.
x=1, y=2 into ①, get z=-1.
10.3
and
⑤-③ get 2z=6, theis z=3.
z=3 into ③, get 4×3+z=13, and get x=1.
the name z=3 into ④, get y=3×3-7, and get y=2.
④ into ①, get x=-2y-1. ⑤
④ and ⑤ into ③ to get
3(2y-1)+2y+3(3y+1)=-5,
Solve y=-1.
y=-1 into ④⑤ to get z=-22, x=1
① and ④ toaof
: (2）①-②, get -3y+4z=1.④
②+③, get -5y+7z=2. ⑤
②④ toaof
①+②, get x-z=0 ④
of ③④ and
and
4、: set x/2=y/3=z/4=kz,
Then x=2k, y=3k, z=4k.
x+y-z=1/12,
So 2k+3k-4k=l/12,
ie k=1/12
So x=1/6, y=1/4, z=1/3.
and
6、:1/3÷x-y+2z)-1/7
(y-2+2z)=1/2-(z-z+2y)=2,
①+②+③, 2x+2y+2z=24.
So z+y+z=12.
1、:you buy zand y,
After , theof theofis in line with theof the .
So, I60and 40.
2、: Let theof the smallfloor tile be x cm and the width be y cm,
After , theof theofis in line with theof the .
So, each floor tile is 45 cm long and 15 cm wide.
14.4
and
1、Tips:theangle on the map tothe ,thewith a scale, andtheto the scale.
2、: as shown in14-4-10
3、: Theis shown in14-4-11
Thefrom point A to point D on the map is 6 cm (1 unit ofon14-4-11 means 1 cm),
Theis 6×60=360 (). Point A is 55° east-south of point D.
and
4、: As shown in14-4-12.
Theboat is 50away from thein theof about 53° to the west of the .
and
5、: A (60°, 20 km), B (0°, 40 km), D (120°, 30 km), E (240°, 40 km).
1、:that there are zinA and yinB,
After , theof theofis in line with theof the .
, theofininA is 64,
Theofwho went toB toinwas 36.
2、: Let the land forbe xand the land forbe y .
After , theof theofis in line with theof the ,
, the farm plans to grow .7and grain 34.8 .
1、: Let theA, B, and C be z, y, 2,
After , theof theofis in line with theof the ,
So, A, B, and C are 12、8、5.
2、: Let this team win, draw, and lose in thisas x, y, and z games, ,
After , theof theofis in line with theof the .
, this team won, drew and lost 6, 3, and 3 gamesin this .
10.4
1、:there are z , y taels of ,
After , theof theofis in line with theof the .
So, there are 6 , 46 taels of .
2、:there are xfromtheand yfromthe .
From theof the title ( dance miao y 锱...,
After , theof theofis in line with theof the .
, theabout 950,000the "11"Week,
About 270,000fromthe .
3、:x kg ofcake and y kg ofcake,
After , theof theofis in line with theof the ,
So, 1,000 kg ofcake and 2,000 kg ofcake are .
4、: Let theof rooms in the hotel be z and theofbe y,
After , theof theofis in line with theof the .
So, theof rooms in the hotel is 8 and theofis 63.
5、: Let thefromin the first half of last year be $x , and thefromin thehalf of the year be $y .
After , theof theofis in line with theof the .
So thebyin the first half of this year is 10×(1+18%)=11.8( US ),
下半年出口创汇额为15×（1+25%）=18.75（亿美元）
6、解：设土豆每千克x元，菠菜每千克y元。
经检验，方程组的解符合题意．
所以，土豆每千克2.2元，菠菜每千克1.8元。
拓展与延伸
7、解：设用z立方米木料做桌面，用y立方米木料做桌腿，由题意得
经检验，方程组的解符合题意．
50×3=150(张)．
所以，用3立方米木料做桌面，用2立方米木料做桌腿，恰好配成方桌150张．