两个不相等的实数m,n满足m²-6m=4,n²-6n=4,求m²+n²-4mn的值.
由题意可知:m、n是x^2-6x-4=0的两根,(分别把m、n代入x²-6x-4=0中,就是m²-6m=4,n²-6n=4)所以m+n=-(-6)=6,mn=-4
m²+n²-4mn
=(m+n)²-6mn
=6²-6×(-4)
=36+24
=60
两个不相等的实数m,n满足m²-6m=4,n²-6n=4,求m²+n²-4mn的值.
由题意可知:m、n是x^2-6x-4=0的两根,(分别把m、n代入x²-6x-4=0中,就是m²-6m=4,n²-6n=4)所以m+n=-(-6)=6,mn=-4
m²+n²-4mn
=(m+n)²-6mn
=6²-6×(-4)
=36+24
=60