Toán Lớp 8: giải phương trình (5x-3)(6x+7)-(3x-4)(4x-3)=(3x+4)(6x-1)-12

Question

Toán Lớp 8:  giải phương trình (5x-3)(6x+7)-(3x-4)(4x-3)=(3x+4)(6x-1)-12

hienthucthu97 · Answer

Answer (5x - 3) . (6x + 7) - (3x - 4) . (4x - 3) = (3x + 4) . (6x - 1) - 12 <=> 30x^2 + 17x - 21 - 12x^2 + 25x - 12 = 18x^2 + 21x - 4 - 12 <=> 30x^2 + 17x - 21 - 12x^2 + 25x - 12 - 18x^2 - 21x + 4 + 12 = 0 <=> (30x^2 - 12x^2 - 18x^2) + (17x + 25x - 21x) + (-21 - 12 + 4 + 12) = 0 <=> (18x^2 - 18x^2) + (42x - 21x) + (-33 + 4 + 12) = 0 <=> 21x + (-29 + 12) = 0 <=> 21x - 17 = 0 <=> 21x = 0 + 17 <=> 21x = 17 <=> x = 17 : 21 <=> x = 17/21 Vậy x = 17/21

dananhnhu2k4 · Answer

Giải đáp:    $(5x-3).(6x+7)-(3x-4).(4x-3)= (3x+4).(6x-1)-12$   $&hArr; (30x&sup2;+35x-18x-21)-(12x&sup2;-9x-16x+12)= (18x&sup2;-3x+24x-4)-12$   $&hArr; 30x&sup2;+17x-21-12x&sup2;+25x-12-18x&sup2;-21x+4+12=0$   $&hArr; (30x&sup2;-12x&sup2;-18x&sup2;)+(17x+25x-21x)+(4+12-21-12)=0$   $&hArr; 21x-17=0$   $&hArr; 21x=17$   $&hArr; x=  dfrac{17}{21}$   $Vậy$ $x= dfrac{17}{21}$