求下列各式的值⒈ (3x^4-2x^3)÷(-x)-(x-x^2)·3x,其中x=-1/2⒉ [(ab+1)(ab-2)

求下列各式的值
⒈ (3x^4-2x^3)÷(-x)-(x-x^2)·3x,其中x=-1/2
=(-3x^3+2x^2)-(3x^2-3x^3)
=5x^2
=5*(-1/2)^2
=5/4
⒉ [(ab+1)(ab-2)-2a^2b^2+2]÷(-ab),其中a=3/2,b=-4/3
=(a^2b^2-ab-2-2a^2b^2+2)/(-ab)
=(a^2b^2+ab)/(ab)
=ab+1
=3/2*(-4/3)+1
=-2+1
=-1
已知(x+y)^2=1,(x-y)^2=49,求x^2+y^2与xy的值
(x+y)^2=x^2+2xy+y^2=1
(x-y)^2=x^2-2xy+y^2=49
x^2+y^2=(1+49)/2=25
xy=(1-49)/4=-12
已知a=b=3,ab=2,求a6^2=b6^2
a6^2什么意思?
是不是这样的：
a+b=3,ab=2
a^2+b^2=(a+b)^2-2ab=3^2-2*2=5