hebeidefeng
春芽
共回答了17个问题采纳率:82.4% 举报
1.已知:a=5,b=239/486,求a^2-5b+ab-5a的值.
a^2-5b+ab-5a
=a*(a+b)-5(a+b)
=(a-5)(a+b)
=(5-5)*(5+239/486)
=0
2.已知x^3+x^2y+xy^2+y^3=5,x^2+y^2=10,求x+y的值.
x^3+x^2y+xy^2+y^3=5
(x+y)(x^2+y^2)=5
(x+y)*10=5
x+y=0.5
3.已知x=a-b,求证:x^2-2ax-b^2+a^2=0.
x=a-b,则x-a=-b
(x-a)^2=x^2-2ax+a^2=(-b)^2
x^2-2ax-b^2+a^2=0
4.已知多项式2x^2-x^2+m有一个因式是2x+1,求m的值.
2x^2-x^2+m
=x^2+m
=(2x+1)(1/2x-1/4)+m+1/4
因此m=-1/4
1年前
5