(x^2+2x-3)/(x^2+3x-10) / (x^2+7x+12)/(x^2-9x+14)

Упростим выражение (x^2 + 2 * x - 3)/(x^2 + 3 * x - 10)/((x^2 + 7 * x  + 12)/(x^2 - 9 * x + 14)); 

(x^2 + 2 * x - 3)/(x^2 + 3 * x - 10) * (x^2 - 9 * x + 14)/(x^2 + 7 * x  + 12); 

(x - (-3)) * (x - 1)/((x - (-5)) * (x - 2)) * ((x - 2) * (x - 7))/((x - (-4)) * (x - (-3)));  

(x + 3) * (x - 1)/((x + 5) * (x - 2)) * ((x - 2) * (x - 7))/((x + 4) * (x + 3)); 

Сократим дробь и тогда останется: 

1 * (x - 1)/((x + 5) * 1) * (1 * (x - 7))/((x + 4) * 1); 

(x - 1)/(x + 5) * (x - 7)/(x + 4); 

(x - 1) * (x - 7)/((x + 5) * (x + 4)).