Question

a) 3x²-8x = 0
b) 8x² = 9x
c)3x²-x² = 0
d)(4x+1).(x+3)=(4x+1).(2x-5) 

Answer 1

a) 3x²-8x = 0
x(3x -8)=0
x= 0
(3x-8)=0
3x-8= 0
3x=+8
x= 8/3
S= 0  e 8/3 

b) 8x² = 9x
8x² -9x = 0
x(8x -9)=0
x= 0
(8x -9)=0
8x -9= 0
8x= +9
x= 9/8

S= 0   e   9/8


c)3x²-x² = 0
x(3x -x )= 0
x= 0
(3x-x)=0
3x -x=0
2x= 0
x= 0/2
x= 0
S= 0

d)(4x+1).(x+3)=(4x+1).(2x-5) 
4x² +12x +x +3 = 8x² -20x +2x -5
4x² -8x² +12x +x +20x -2x +3 +5=0
-4x² +31x +8=0  .(-1)
4x² -31x -8=0

a= 4     b= -31      c= -8
▲= b² -4.a.c= (-31)² -4.(4). (-8)= 961 +128= 1089

x= (-b ± √▲)/2.a
x= (-(-31) ± √ 1089)/2.4
x= (+31 ± 33)/8
x'= (+31+ 33)/8= 64/8= 8
x"=(+31 -33)/8= -2/8 = -1/4

S= 8   e -1/4