Question

put the value in the following equation
i)3x^2-5x+109(x=1/root 2)
ii)3x^2+5/2x-7 (x=2/root3)
iii)7x^2+5x-9 (x= -1/5)

Answer 1

1. 108 ans.
2. 5(√3-2)/2
3. -243/25

Answer 2

Solution-

i-

The given equation is,

$3x^2-5x+109$

$=3(\frac{1}{\sqrt{2}})^2-5(\frac{1}{\sqrt{2}})+109$

$=3(\frac{1}{2})-5(\frac{1}{\sqrt{2}})+109$

$=1.5-3.535+109$

$=106.965$

ii-

The given equation is,

$3x^2+\frac{5}{2}x- 7$

$=3(\frac{2}{\sqrt{3}})^2+\frac{5}{2}(\frac{2}{\sqrt{3}})- 7$

$=3(\frac{4}{3})+\frac{5}{2}(\frac{2}{\sqrt{3}})- 7$

$=4+2.886- 7$

$=-0.114$

iii.

$7x^2+5x-9$

$=7(-\frac{1}{5})^2+5(-\frac{1}{5})-9$

$=7(\frac{1}{25})-5(\frac{1}{5})-9$

$=0.28-1-9$

$=-9.72$