分析:(1)先去括號化簡,再根據(jù)有理數(shù)的加減混合運(yùn)算法則計(jì)算即可;
(2)先計(jì)算乘方和絕對值,再算乘除,最后計(jì)算加減;
(3)先去括號,再合并同類項(xiàng)即可;
(4)先去括號,合并同類項(xiàng)化簡代數(shù)式,再代值計(jì)算即可.
解答:解:(1)12-(-18)+(-7)-15
=12+18-7-15
=8;
(2))-2
2+(-3)×|-4|-(-3)
2÷(-2)
=-4-3×4+9÷2
=-4-12+4
=
-;
(3)-x-2(2x-3)+(3x+5)
=-x-4x+6+3x+5
=-x-4x+3x+6+5
=-2x+11;
(4)3(x
2-2xy)-[3x
2-2y+2(xy+y)]
=3x
2-6xy-[3x
2-2y+2xy+2y]
=3x
2-6xy-3x
2+2y-2xy-2y
=-8xy,
當(dāng)
x=-、y=-3時,-8xy=-8×(-
)×(-3)=-12.
點(diǎn)評:考查了有理數(shù)的混合運(yùn)算和整式的加減-化簡求值,解題的關(guān)鍵是對運(yùn)算順序和運(yùn)算法則的掌握,是基礎(chǔ)計(jì)算題型.