petit 18 ) et petit 19 ) STP

19)
2x+5 = 7(x-4)
2x +5= 7x -28
2x = 7x-28-5
2x = 7x -33
33= 7x-2x
33= 5x
33/5=x
6.6.= x

x²=18
x*x=18
x=18x

(2x+5)(4-7x)=0
(8x-14x +20-35x)= 0
(-41x+20) =0
20 = 41x
20/41 = x
0.48 =x

bonjour

A = √150 + 4 √6 - 2√54
a = 5√6 + 4√6 - 3√6 = 6√6

a ) 2 x + 5 = 7 x - 28
     2 x - 7 x = - 28 - 5
    - 5 x = - 33
         x = 33/5

b) x² = 18
     x = √18 ou - √18

c) ( 2 x +5) ( 4 - 7 x) = 0
soit 2 x +5 = 0
       2x = - 5 et x = - 5/2

soit 4 - 7 x = 0
      - 7 x = - 4 et x = 4/7