Question

化简求值:(x+5)平方-（x-5)平方-5(2x+1)(2x-1)+x乘以（2x-1)平方，其中x=-1

化简求值:(x+5)平方-（x-5)平方-5(2x+1)(2x-1)+x乘以（2x-1)平方，其中x=-1

Answer 1

解：
原式
=(x+5+x-5)(x+5-x+5)-5(4x²-1)+x(4x²-4x+1)
=2x·10-20x²+5+4x³-4x²+x
=4x³-4x²-20x²+x+20x+5
=4x³-24x²+21x+5
=4×(-1)-24×1+21×(-1)+5
=-4-24-21+5
=-44

Answer 2

原式=[(x+5)+(x-5)][(x+5)-(x-5)]-(2x-1)[5(2x+1)-x(2x-1)]
=2x*10-(2x-1)(10x+5-2x^2+x)
=20x-(2x-1)(5+11x-2x^2)
=20*(-1)-[2*(-1)-1]*[5+11*(-1)-2*(-1)^2]
=-20-(-3)*(-8)
=-20-24
=-44