Đáp án:
Giải thích các bước giải:
Bài 1 :
d)
<=> 4x^2 - 10x = 4x^2 + 4x = 11
<=> -10x = 4x + 11
<=> -10x - 4x = 11
<=> -14x = 11
<=> x = -11/14
e)
<=> x^2 - 4x + 4 - 9 = 0
<=> x^2 + x - 5x - 5 = 0
<=> x ( x + 1 ) - 5 ( x + 1 ) = 0
<=> ( x + 1 ) ( x - 5 ) = 0
Th1 : x + 1 = 0
x = -1
TH2 : x - 5 = 0
x =5
f)
<=> 4x - 20 = 7x^2 - 35x
<=> 4x - 20 - 7x^2 + 35x = 0
<=> 39x - 20 - 7x^2 = 0
<=> -39x + 20 + 7x^2 = 0
<=> 7x^2 - 39x + 20 = 0
<=> 7x^2 - 4x - 35x + 20 = 0
<=> x ( 7x - 4 ) - 5 ( 7x - 4 ) = 0
<=> ( 7x - 4 ) ( x - 5 ) = 0
TH1 : 7x - 4 = 0
x = 4/7
Th2 : x - 5 = 0
x = 5