m+n=20,又已知m+2q=18 ,求代数式(3n-6q)(3n-6q)-2/10q-5n.

m+n=20 n=20-m
m+2q=18 2q=18-m
(3n-6q)(3n-6q)-2/(10q-5n)
=(60-3m-54+3m)(60-3m-54+3m)-2/(90-5m-100+5m)
=6*6-2/(-10)
=36+1/5
=181/5

∵m+n=20 m+2q=18
m=20-n m=18-2q
∴20-n=18-2q
n-2q=2
∴(3n-6q)(3n-6q)-2/10q-5n
=3(n-2q)²+5(n-2q)/2
=3*2²+5×2/2
=12+5
=17