Сократите дробь (16x^2+16x-21) / (-20x^2+23x-6) и найдите её значение при x=5/13

16x²+16x-21=16 (x+7/4) (x-3/4) = (4x+7) (4x-3)

D=256+1344=1600

x1 = (-16-40) / 32=-7/4

x2 = (-16+40) / 32=3/4

-20x²+23x-6=-20 (x-3/4) (x-2/5) = - (4x-3) (5x-2) = (4x-3) (2-5x)

D=529-480=49

x1 = (-23-7) / (-40) = 3/4

x2 = (-23+7) / (-40) = 2/5

(4x+7) (4x-3) / [ (4x-3) (2-5x) = (4x+7) / (2-5x)

x=5/13

(4*5/13+7) : (2-5*5/13) = (20+91) / 13*13 / (26-25) = 111/1=111