1、x²-5x=14,即x²-5x-14=0,即(x+2)(x-7)=0,解得x=-2,x=7
(x-10)(2x-1)-(x+1)²=(2x²-21x+10)-(x²+2x+1)=x²-23x+9 (1)
将x=-2代入(1)式,得(-2)²-23*(-2)+9=4+46+9=59
将x=7代入(1)式,得7²-23*7+9=49-161+9=103
2、a、b互为相反数,c、d互为倒数,m的绝对值为2
即a+b=0,c/d=1((cd)^-1),|m|=2(m=2,m=-2)
(a+b)(a-b)+(cd)^-1÷(1-2m+m²)=0*(a-b)+(1)^-1÷(1-2m+m²)=1/(1-2m+m²) (2)
将x=-2代入(2)式,得1/(1-2*(-2)+(-2)²)=1/9
将x=2代入(2)式,得1/(1-2*2+2²)=1
3、x-3y=4,x*y=5/2
(x+3y)²=(x-3y)²+12xy=4²+12*5/2=16+30=46