Please help on quadradics

**sjallim** · October 19th 2006, 02:18 PM

3x+3/4-2(x-5)=30

(2X*2X)-12X+9=0 USE FACTORISATION

(3X*3X)+13X+2=0 STATE ANSWER TO THREE SIGNIFICANT NUMBERS

X/8+3X/16=5/X

(X*X)-2X-6=0

**OReilly** · October 19th 2006, 02:53 PM

Originally Posted by sjallim

3x+3/4-2(x-5)=30

(2X*2X)-12X+9=0 USE FACTORISATION

(3X*3X)+13X+2=0 STATE ANSWER TO THREE SIGNIFICANT NUMBERS

X/8+3X/16=5/X

(X*X)-2X-6=0

1)
$\begin{array}{l} 3x + \frac{3}{4} - 2(x - 5) = 30 \\ 3x + \frac{3}{4} - 2x + 10 = 30 \\ x = 20 - \frac{3}{4} \\ x = \frac{{77}}{4} \\ \end{array} $

2)
$\begin{array}{l} (2x*2x) - 12x + 9 = 0 \\ 4x^2 - 12x + 9 = 0 \\ (2x - 3)^2 = 0 \\ \\ 2x - 3 = 0 \\ 2x = 3 \\ x = \frac{3}{2} \\ \end{array} $

3)
$\begin{array}{l} (3x*3x) + 13x + 2 = 0 \\ 9x^2 + 13x + 2 = 0 \\ x_{1/2} = \frac{{ - 13 \pm \sqrt {97} }}{{18}} \\ \end{array} $

4)
$\begin{array}{l} \frac{x}{8} + \frac{{3x}}{{16}} = \frac{5}{x} \\ \frac{{2x + 3x}}{{16}} = \frac{5}{x} \\ \frac{{5x}}{{16}} = \frac{5}{x} \\ 5x^2 = 80 \\ x^2 = 16 \\ x = \sqrt {16} \\ x = 4 \\ \end{array} $

5)
$\begin{array}{l} (x*x) - 2x - 6 = 0 \\ x^2 - 2x - 6 = 0 \\ x_{1/2} = \frac{{2 \pm \sqrt {4 + 24} }}{2} = \frac{{2 \pm \sqrt {28} }}{2} \\ \end{array} $

I didn't calculate 3) and 5), hopefully you can do that.

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