If the equation MX + 3 − nx − 3 = 8xx2 − 9 holds for all real numbers x except ± 3, then the value of Mn is () A. 8B. -8C. 16D. -16

If the equation MX + 3 − nx − 3 = 8xx2 − 9 holds for all real numbers x except ± 3, then the value of Mn is () A. 8B. -8C. 16D. -16

∵ MX + 3-nx − 3 = 8xx2 − 9, ∵ m (x − 3) − n (x + 3) x2 − 9 = 8xx2 − 9, that is: (m − n) x − 3 (M + n) x2 − 9 = 8xx2 − 9 ∵ m − n = 8m + n = 0, that is, M = 4, n = - 4. ∵ Mn = - 16

If M / x + 3-N / x-3 = 8x / X & sup2; - 9 (x ≠ plus or minus 3), find the value of Mn, the answer is - 16, but when m is 12 and N is 1, there is x, and X is 13

m/(x+3)-n/(x-3)=(m(x-3)-n(x+3))/(x²-9)=((m-n)x-(3m+3n))/(x²-9)=8x/(x²-9);
∴3m+3n=0;
m-n=8;
∴2m=8;
m=4;
n=-4;
∴mn=4×(-4)=-16;
If you don't understand this question, you can ask,

If M + n = 5, Mn = - 3, then 1 M2 + 1 N2=______ ．

∵ m + n = 5, Mn = - 3, ∵ 1m2 + 1n2 = N2 + m2m2n2 = (M + n) 2 − 2Mn (MN) 2 = 52 − 2 × (− 3) (− 3) 2 = 319