t2 5t 84 0 12 7 12 7 12 1 xx 2 35 0 2 5 7 5 7Solution41

t^2 + 5t - 84 = 0 12, 7 12, -7 -12, 1 x(x - 2) = 35 0, 2 5, -7 -5, 7

Solution

41) t^2 +5t -84 =0

factorise : t^2 +12t -7t -84=0

t( t +12) -7(t +12) =0

(t -7)(t +12) =0

t = 7 ; t = -12

42) x(x -2) = 35

x^2 -2x -35 =0

x^2 -7x +5x -35 =0

x( x-7) + 5( x-7) =0

(x+5)(x-7) =0

x=-5 ; x=7