Đáp án:
Giải thích các bước giải:
b2
a)3/7 + 1/7 : x = 3/14 b) 11/3 + 26/7.x = 3/2
1/7 : x = 3/14 - 3/7 26/7.x = 3/2 - 11/3
1/7 : x = 3/14 - 6/14 26/7.x = 9/6 - 22/6
1/7 : x = -3/14 26/7.x = -13/6
x = -3/14 . 1/7 x = -13/6 : 26/7
x = -3/98 x = -13/6 . 7/26
x = -7/12
c) x +3,5 - 4/7 = 1/2 - 4 1/8 d) 7,2x + ( -3,7.x) -2,7 = 7,8
x + 7/2 - 4/7 = 1/2 - 33/8 7,2x + ( -3,7.x) = 7,8 + 2,7
x + 7/2 - 4/7 = 4/8 - 33/8 7,2x + ( -3,7.x) = 10,5
x + 7/2 - 4/7 = -29/8 -3,7.x = 10,5 : 7,2
x + 7/2 = -29/8 + 4/7 -3,7x = 35/24
x + 7/2 = -203/56 + 32/56 x = 35/24 : (-3,7)
x + 7/2 = -171/56 x = 35/24 . 1/-3,7
x = -171/56 - 7/2 x = -175/444
x = -171/56 - 196/56
x = -367/56
e) 3( x-1/2) - 5(x+3/5) = -x +1/5 g) (1/4 - x) (x+ 2/5) = 0
3x - 3/2 - 5(x+3/5) = -x +1/5 => 1/4 -x = 0 hoặc x + 2/5 = 0
3x - 3/2 - 5x - 3 = -x +1/5 => x = 11/4 hoặc x = -2/5
3x - 9/2 - 5x = -x +1/5
-2x - 9/2 = -x +1/5
-2x - 9/2 + 9/2 = -x +1/5 + 9/2 h) 1/4.x^2 - 3x = 0
-2x = -x + 47/10 1x^2/4 - 3𝑥=0
-2x + x = -x + 47/10 + x x^2/4 - 3𝑥=0
-x = -x + 47/10 + x x^2/4 + 4(-3)x/4 = 0
-x = 47/10 𝑥^2+4(−3)𝑥/4=0
-x/-1 = 47/10 /-1 𝑥^2−12𝑥/4=0
x = 47/10 / -1 4 . 𝑥^2−12𝑥/4=0
x = -47/10 𝑥^2−12𝑥=0
i) |2x+1| +2/3 = 2 j) |2x-3| + | y -5| = 0
|2x+1| = 2 - 2/3 => 2x-3 = 0 hoặc y-5=0
|2x+1| = 4/3 => x= -1 hoặc y = 5
=> 2x+1 = 4/3 hoặc 2x+1 = -4/3
=> x = 1/6 hoặc x = -7/6
k) ( 2x-3)^2 = 36 l) 7^x+2.7^x = 357
(2𝑥−3)(2𝑥−3)=36 7^x.1 + 2. 7^x=357
2𝑥(2𝑥−3)−3(2𝑥−3)=36 7^x . (1+2) = 357
4𝑥2−6𝑥−3(2𝑥−3)=36 7^x . 3 =357
4𝑥2−6𝑥−6𝑥+9=36 7^x = 357: 3
4𝑥2−12𝑥+9=36 7^x = 119
4𝑥2−12𝑥+9−36=0 =>
4𝑥2−12𝑥−27=0
