【1.x(x+1)(x+2)(x+3)+12.x³+x²-5x-63.z²+3x²-9x-274.已知a²+2a-14=0,求(a-3)(a+6)(a+5)(a-4)+20的值就这些就算有一个答案也好啊~】
1.x(x+1)(x+2)(x+3)+1
2.x³+x²-5x-6
3.z²+3x²-9x-27
4.已知a²+2a-14=0,求(a-3)(a+6)(a+5)(a-4)+20的值
就这些就算有一个答案也好啊~
1.x(x+1)(x+2)(x+3)+1
=(x²+3x)(x²+3x+2)+1
=(x²+3x)²+2(x²+3x)+1
=(x²+3x+1)²
2.x³+x²-5x-6
=x³+x²-2x-3x-6
=x(x²+x-2)-3(x+2)
=x(x-1)(x+2)-3(x+2)
=(x+2)(x²-x-3)
3.x³+3x²-9x-27
=x²(x+3)-9(x+3)
=(x+3)(x²-9)
=(x+3)²(x-3)
4.已知a²+2a-14=0,求(a-3)(a+6)(a+5)(a-4)+20的值
(a-3)(a+6)(a+5)(a-4)+20
=(a²+2a-15)(a²+2a-24)+20
=(14-15)(14-24)+20
=-1×(-10)+20
=10+20
=30
