Use the trial and improvement method to solve the equation 2xcubed+5=24. Find a solution that is a positive number give your answer correct to one decimal place

Question

Use the trial and improvement method to solve the equation 2xcubed+5=24. Find a solution that is a positive number give your answer correct to one decimal place. 

ease help and show working out, thank you!

Answer 1

Hi Kath;

2x³+5=24

Let's subtract 5 from both sides...

-5+2x³+5=24-5

2x³=19

Let's divide both sides by 2...

(2x³)/2=19/2

x³=9.5

 

x   | x³ | result

1   | 1   |too small

2   | 8   |very close

2.1| 9.3|closest

2.2|10.6|too high

 

x=2.1