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電子課本網(wǎng) 第29頁

第29頁

信息發(fā)布者:
?$ =(4x^2-1)(4x^2+1)$?
?$=16x^4-1$?
?$ =[(2m+3n)(3n-2m)]^2$?
?$=(9n^2-4\ \mathrm {m^2})^2$?
?$=81n^4-72\ \mathrm {m^2}n^2+16m^4$?
?$ =4x^2-y^2-4x^2+4xy-y^2$?
?$=4xy-2y^2$?
?$ =(x-y)^2-1^2$?
?$=x^2-2xy+y^2-1$?
解:?$Q=(\mathrm {m^2}+1-m)(\mathrm {m^2}+1+m)=(\mathrm {m^2}+1)^2-\mathrm {m^2}$?
?$=m^4+2\ \mathrm {m^2}+1-\mathrm {m^2}=m^4+\mathrm {m^2}+1$?
?$P=[(m+1)(m-1)]^2=[\mathrm {m^2}-1]^2=m^4-2\ \mathrm {m^2}+1$?
∵?$m≠0$?
∴?$\mathrm {m^2}>0$?
∴?$Q-P=m^4+\mathrm {m^2}+1-m^4+2\ \mathrm {m^2}-1=3\ \mathrm {m^2}>0$?
∴?$Q>P$?