Question

a) X²-(x+10)²
b)(2x-1)²+x(3x-2)
c) (3x+5)²-9x2
d) (1+x).(1-x)-(1+x)²

Answer 1

a)

x²-(x+10)² =

x² - (x + 10 ) . (x + 10) =

x² - (x² + 10x+10x + 10²) =

x² - (x² + 20x + 10²) =

x² - x² - 20x - 10² =

  0      - 20x -100 =

- 20 x - 100 =

-20x = 100

-x = 100 /20

-x = 5 . (-1)

x = 5

b)

(2x-1)²+x(3x-2) =

(2x-1).(2x-1) + x . (3x-2) =

4x² -2x -2x +1² + x . (3x-2) =

4x² - 4x + 1 +        3x² - 2x = arrumado

4x² + 3x² -4x-2x + 1 =

     7x² - 6x + 1

c)

(3x+5)²-9x² =

(3x+5).(3x+5) - 9x² =

9x²+15x+15x+5² - 9x² =

9x² +30x + 25 - 9x² = arrumando

9x² - 9x² + 30x + 25 =

    0     + 30x + 25 =

30x + 25 =

30x = -25

x =  $-\frac{25}{30}$

x = $-\frac{25:5}{30:5}$

x = $-\frac{5}{6}$

d)

(1+x).(1-x)-(1+x)² =

(1+x) . (1+x) - (1+x) . (1+x) =

1² +x+x+x² - (1² +x+x +x²) =

1² +2x +x² - (1² +2x +x² ) =

1 +2x +x² - 1 -2x - x² = arrumando

1 - 1 + 2x - 2x + x² - x² =

0     +  0         +    0      =

        0