Question

Calcule :
A) 7x² + 2 (x²-1)
B) 10 - 4 ( x - 3 ) + 5
C) -9 ( 2x -1 ) + 15x
D) 0,25 ( 4x - 100 ) + 7x
E) 3a² - a ( 2a - 7 ) + 1
F) 5 ( 1/5 + x ) - 3x - 10

Answer 1

A) 7x^2+2(x^2-1)
7x^2+2x^2-2
9x^2-2
x^2=2/9
x=+,-\/2/9
x=+,-\/2/3

B)10-4(x-3)+5
10-4x-12+5
10-4x-17
-4x-17+10
-4x-7=0
-4x=7
-x=7/4
-x=1,75(-1)
x=1,75

C)-9(2x-1)+15x
-18x+9+15x
-18x+15x+9=0
-3x=-9
-x=-9/3
-x=-3(-1)
x=3

D)0,25(4x-100)+7x
x-25+7x
x+7x-25=0
8x=25
x=25/8
x=3,125
x=3,13

E)3a^2-a(2a-7)+1
3a^2-2a^2-7a+1
a^2-7a+1=0
a=1. b=-7. c=1
delta=b^2-4ac
delta=(-7)^2-4(1)(1)
delta=49-4
delta=45
x=-b+,-\/delta/2a
x=-(-7)+,;\/45/2(1)
x=7+,- 6,70/2
x1=7+6,70/2》x1=13,70/2》x1=6,85
x2=7-6,70/2》x2=0,30/2》x2=0,15