Question

Which quadratic equation has roots –2 and 1/5?

Answer 1

Answer:

The equation $5x^2\:+\:9x\:-\:2\:=\:0$ has roots –2 and 1/5.

Hence, the option 'a' is the correct answer.

Step-by-step explanation:

Checking the equation

$5x^2\:+\:9x\:-\:2\:=\:0$

putting x = -2 in the equation

$5\left(-2\right)^2\:+\:9\left(-2\right)-\:2\:=\:0\:$

$2^2\cdot \:\:5-9\cdot \:\:2-2=0$

$2^2\cdot \:5-18-2=0$

$20-20=0$

$0=0$

L.H.S=R.H.S

putting x = 1/5 in the equation

$5\left(\frac{1}{5}\right)^2\:+\:9\left(\frac{1}{5}\right)-\:2\:=\:0\:$

$5\left(\frac{1}{5}\right)^2+9\cdot \:\frac{1}{5}-2=0$

$\frac{1}{5}+\frac{9}{5}-2=0$

$2-2=0$

$0=0$

L.H.S=R.H.S

As putting x = -2 and x = 1/5 satisfy the equation.

Therefore, the equation $5x^2\:+\:9x\:-\:2\:=\:0$ has roots –2 and 1/5.

Hence, the option 'a' is the correct answer.