a,(3x-1)(x+3)=(2-x)(5-3x) c,(x+1)(x+9)=(x+3)(x+5)
b,(x+5)(2x-1)=(2x-3)(x+1) d,(3x+5)(2x+1)=(6x-2)(x-3)
a,(3x-1)(x+3)=(2-x)(5-3x) c,(x+1)(x+9)=(x+3)(x+5) b,(x+5)(2x-1)=(2x-3)(x+1) d,(3x+5)(2x+1)=(6x-2)(x-3)
By Jade
a) (3x – 1)(x + 3) = (2 – x)(5 – 3x)
3x² + 9x – x – 3 = 10 – 6x – 5x + 3x²
3x² – 3x² + 9x – x + 6x + 5x = 10 + 3
19x = 13
x = $\frac{13}{19}$
Vậy x = $\frac{13}{19}$
b) (x + 5)(2x – 1) = (2x – 3)(x + 1)
2x² – x + 10x – 5 = 2x² + 2x – 3x – 3
2x² – 2x² – x + 10x – 2x + 3x = -3 + 5
10x = 2
x = 2 : 10
x = 0,2
Vậy x = 0,2
c) (x + 1)(x + 9) = (x + 3)(x + 5)
x² + 9x + x + 9 = x² + 5x + 3x + 15
x² – x² + 9x + x – 5x – 3x = 15 – 9
2x = 6
x = 6 : 2
x = 3
Vậy x = 3
d) (3x + 5)(2x + 1) = (6x – 2)(x – 3)
6x² + 3x + 10x + 5 = 6x² – 18x – 2x + 6
6x² – 6x² + 3x + 10x + 18x + 2x = 6 – 5
33x = 1
x = $\frac{1}{33}$
Vậy x = $\frac{1}{33}$
Đáp án:
a, x = 13/19
b, x = 3
c, x = 1/5
d, x = 1/33
Giải thích các bước giải:
a, (3x – 1)(x + 3) = (2 – x)(5 – 3x)
<=> 3x² + 8x – 3 = 3x² – 11x + 10
<=> 3x² + 8x – 3x² + 11x = 10 + 3
<=> 19x = 13
<=> x = 13/19
b, (x + 1)(x + 9) = (x + 3)(x + 5)
<=> x² + 10x + 9 = x² + 8x + 15
<=> x² + 10x – x² – 8x = 15 – 9
<=> 2x = 6
<=> x = 3
c, (x + 5)(2x – 1) = (2x – 3)(x + 1)
<=> 2x² + 9x – 5 = 2x² – x – 3
<=> 2x² + 9x – 2x² + x = – 3 + 5
<=> 10x = 2
<=> x = 1/5
d, (3x + 5)(2x + 1) = (6x – 2)(x – 3)
<=> 6x² + 13x + 5 = 6x² – 20x + 6
<=> 6x² + 13x – 6x² + 20x = 6 – 5
<=> 33x = 1
<=> x = 1/33