x2+mx-12=(x+3)(x+n),则常数m= ,n=

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x2+mx-12=(x+3)(x+n),则常数m= ,n=

x2+mx-12=(x+3)(x+n),则常数m= ,n=
x2+mx-12=(x+3)(x+n),则常数m= ,n=

x2+mx-12=(x+3)(x+n),则常数m= ,n=
x²+mx-12=(x+3)(x+n) = x² + 2x + nx + 3n
所以3n = -12,n = -4
2 + n = m,m = -2

用待定系数法,m=-2 n=-4

解答如下:
x²+mx-12=(x+3)(x+n) = x² + 2x + nx + 3n
所以3n = -12,n = -4
2 + n = m,m = -2

化简得x²+mx-12=x²+3x+nx+3n即mx-12=(3+n)x+3n
3n=-12,3+n=m;n=-4,m=-1