Hi Admin,

I have created VF page & controller class for you & displayed two button on custom page savewithtask & savewithouttask. When you will fill account & task information and click on savewithtask  button. Account will be created with task.
If you will fill only account information and click on savewithouttask button thenn account will be created without task.
Please use vf page & class. 

If you want to more fields for account & task information then add your fields in VF page.

Controller class:
 

public class accountController {

   
   Account account;
   Task Task;
   


 
   public Account getAccount() {
      if(account == null) account = new Account();
      return account;
   }

   public Task getTask() {
      if(Task == null) task = new Task();
      return task;
   }

  

   public PageReference savewithtask() {
   
      insert account;

      
      task.whatId = account.id;
      insert task;

  

      PageReference accPage = new ApexPages.StandardController(Account).view();
      accPage.setRedirect(true);

      return accPage;
   }
   
   public PageReference savewithouttask() {

      insert account;

      PageReference accPage = new ApexPages.StandardController(Account).view();
      accPage.setRedirect(true);

      return accPage;
   }

}

VF Page:

<apex:page controller="accountController" tabStyle="Account">
 
  <apex:sectionHeader title="New Account"/>
    <apex:form >
      <apex:pageBlock title="Account Information" mode="edit">
        <apex:pageBlockButtons >
          <apex:commandButton action="{!savewithtask}" value="savewithtask"/>
          <apex:commandButton action="{!savewithouttask}" value="savewithouttask" />
                              
        </apex:pageBlockButtons>
      <apex:pageBlockSection title="Account Information">

        <!-- Within a pageBlockSection, inputFields always display with their
             corresponding output label. -->
        <apex:inputField id="accountName" value="{!account.name}" required="false"/>
        <apex:inputField id="accountSite" value="{!account.site}"/>
      </apex:pageBlockSection>
      <apex:pageBlockSection title="Task Information">
        <apex:inputField id="Subject" value="{!Task.Subject}" required="false"/>
        <apex:inputField id="Status" value="{!Task.Status}" required="false"/>
        
      </apex:pageBlockSection>
    </apex:pageBlock>
  </apex:form>
</apex:page>

If you have any query please let me know.

If this post solves your problem kindly mark it as solution.

Thanks,
Arvind Kumar