f.3代入法(方程)

16w=5-4s--------(1)
3s-8=8w+7--------(2)
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w=5-4s/16---------(3)

(3)代入(2)
3s-8=8(5-4s/16)+7
3s-8=40-32s/16+7
3s-15=40-32s/16
48s-240=40-32s
80s=280
s=3.5--------------(4)
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(4)代入(1)
16w=5-4(3.5)
16w=5-14
16w=-9
w= -9/16


答案=s=3.5
w= -9/16

16w = 5 - 4s --- 1
3s - 8 = 8w + 7 --- 2
From 1:
w = (5 - 4s) / 16 --- 3
substitute 3 into 2:
3s - 8 = 8 [(5 - 4s) / 16] + 7
3s - 8 = (5 - 4s) / 2 + 7
6s - 16 = 5 - 4s + 14
6s + 4s = 14 + 5 + 16
10s = 35
s = 3.5
substitute s = 3.5 into 3
w = [5 - 4(3.5)] / 16
w = (5 - 14) / 16
w = -9 / 16
w = - 0.5625

16w=5-4s-----------------------(1)
3s-8=8w+7--------------------(2)

(2)x2, (3s-8)x2=(8w+7)x2
6s-16=16w+14

∵16w=5-4s
6s-16=(5-4s)+14
6s+4s=5+14+16
10s=35
s=35/10=7/2

16w=5-4s
16w=5-4(7/2)
16w=5-14
16w=-9
w= -9/16

16w=5-4s-----(1)
3s-8=8w+7------(2)
由(1)
w=(5-4s)/16------(3)
代(3)入(2)
3s-8=8[(5-4s)/16]+7
3s-8=[(5-4s)/2]+7
3s-[(5-4s)/2]=7+8
6s/2-[(5-4s)/2]=7+8
6s-5+4s/2=15
6s-5+4s=30
10s=35
s=3.5
代s=3.5入(1)
16w=5-4(3.5)
16w=-9
w=-9/16

w=(5-4s)/16
3s-8=8[(5-4s)/16]+7
3s-8=(5-4s)/2+7
6s-16=5-4s+14
10s=35
s=3.5

16w=5-4*3.5
w=-0.5625