creating form input field

<mat-card>
        <mat-card-content>
          <form class="example-form" [formGroup]="customerForm">
            <mat-form-field class="example-full-width">
              <input type="text" matInput formControlName="firstName" placeholder="FirstName">
            </mat-form-field>

            <mat-form-field class="example-full-width">
              <input type="text" matInput formControlName="lastName" placeholder="Last Name">
            </mat-form-field>

            <mat-card>
              <button type="submit" mat-raised-button color="primary" (click)="addMobile()">
                Add More Number </button>
              <br>
              <br>
              <div formArrayName="mobiles" *ngFor="let leg of mobiles.controls; let i= index;">
                <div [formGroupName]="i">
                  <mat-form-field class="example-full-width">
                    <input type="number" matInput placeholder="Mobile Number" formControlName="number">
                  </mat-form-field>
                  <button type="button" mat-raised-button color="accent" (click)="removeMobile(i)"> Remove</button>
                </div>

              </div>
            </mat-card>

            <button type="button" mat-raised-button color="primary" (click)="save()" [disabled]="!customerForm.valid">
              Save</button>

          </form>
        </mat-card-content>
      </mat-card>