数学题:求值（能化简的先化简再求值，请看补充谢谢。）
\u8c01\u80fd\u5e2e\u6211\u627e20\u9053\u5316\u7b80\u6c42\u503c\u7684\u6570\u5b66\u989810a(5\u4e58\u4ee5a\u7684\u5e73\u65b9-b)-2a(5b+25\u4e58\u4ee5a\u7684\u5e73\u65b9\uff09\uff0d3ab,\u5176\u4e2da=1,b=1/23.
1/3x^3-2x^2+2/3x^3+3x^2+5x-4x+7,(x=2)
\u5148\u5316\u7b80,\u518d\u6c42\u503c.
5abc-{2a²b[3abc-(4ab²-a²b)]-2ab²}\u5176\u4e2da=-2,b=3,c=-1/4.
\u5df2\u77e5a²+a-1=0,\u6c42\u4ee3\u6570\u5f0fa³+2a²+5\u7684\u503c.
\uff0e(a+2)\u7684\u4e8c\u6b21\u65b9-(a-1)(a+1),\u5176\u4e2da\uff1d3\uff0e25
\u5148\u5316\u7b80\u518d\u6c42\u503c
\uff08X-1)\u7684\u4e8c\u6b21\u65b9+(x+3)(x-3)+(x-3)(x-1),\u5176\u4e2dX\u7684\u4e8c\u6b21\u65b9-2x=2
\u5df2\u77e5:a+b=12,a\u7684\u5e73\u65b9+b\u7684\u5e73\u65b9=74
\u6c42ab\u7684\u503c
2.(x+y-2)(x-y+2)
3.\u5148\u5316\u7b80,\u518d\u6c42\u503c
(4x-3y)\u7684\u5e73\u65b9-(3x-2y)(3x+2y),\u5176\u4e2dx=2,y=1
\u5148\u5316\u7b80\uff0c\u518d\u6c42\u503c
1\u30015ac-2a^2b+[3abc-\uff084ab^2-a^2b\uff09]\uff0c\u5176\u4e2da=-2\uff0cb=-1\uff0cc=3\u3002
\u89e3\uff1a5ac-2a^2b+3abc-4ab^2+a^2b
=5ac-a^2b+3abc-4ab^2
\u5f53a=-2\uff0cb=-1\uff0cc=3\u65f6\uff0c
5ac-a^2b+3abc-4ab^2=5\u00d7(-2)\u00d73-(-2)^2\u00d7(-1)+3\u00d7(-2)\u00d7(-1)\u00d73-4\u00d7(-2)\u00d7(-1)^2=-30+4+18-8=44
2\u3001\u5df2\u77e5a+b=2,\u6c422(a^2+3a-2b+2b^2\uff09-\uff082a^2+4a-6b+4b^2\uff09\u7684\u503c\u3002
2a^2+6a-4b+4b^2-2a^2-4a+6b-4b^2
=2a+2b
\u5f53a+b=2\u65f6\uff0c
2a+2b=2\uff08a+b\uff09=2\u00d72=4
当a=5时，代入=7*5*9-3+7*5=35*9-3+35=315+32=347
当x=2.4， b=0.3时，化简=5a+4y的二次方 代入=5*2.4+4*0.3的二次方=12+4*0.3*0.3=12+0.09*4=12+0.36=12.36
当a=6.2b=1.2时，代入=6.2*6.2-15=38.44-15=23.44
当a=4时，代入=7*4*9-3+7*4=28*9-3+28=252+25=277
当a=5时，代入=7*5*9-3+7*5=35*9-3+35=315+32=347
当x=2.4， b=0.3时，化简=5a+4y的二次方 代入=5*2.4+4*0.3的二次方=12+4*0.3*0.3=12+0.09*4=12+0.36=12.36
当a=6.2b=1.2时，代入=6.2*6.2-15=38.44-15=23.44
（1）当a=4时，7*4*9-3+7*4=277
（2）当a=5时，7*5*9-3+7*5=347
2. 当a=2.4，b=0.3时，5*2.4+4* 0.3*0.3=12.36
3. 当a=6.2，b=1.2时，6.2*6.2-15=23.44
7a×9－3+7a=7a×(9+1)-3=7×4,5×10-3=312
5a－2y²+6y²=5a+4y²=你这太乱了，什么a,x,y的啊
什么意思，没看出来
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