diff --git a/apps/regression/model/cubic_model.cpp b/apps/regression/model/cubic_model.cpp
index 4acbd07b2..5a2e4671e 100644
--- a/apps/regression/model/cubic_model.cpp
+++ b/apps/regression/model/cubic_model.cpp
@@ -39,10 +39,6 @@ ExpressionLayout * CubicModel::layout() {
 }
 
 Expression * CubicModel::simplifiedExpression(double * modelCoefficients, Poincare::Context * context) {
-  if (m_expression != nullptr) {
-    delete m_expression;
-    m_expression = nullptr;
-  }
   double a = modelCoefficients[0];
   double b = modelCoefficients[1];
   double c = modelCoefficients[2];
@@ -67,9 +63,9 @@ Expression * CubicModel::simplifiedExpression(double * modelCoefficients, Poinca
     false);
   Expression * dExpression = new Decimal(d);
   Expression * const operands[] = {ax3Expression, bx2Expression, cxExpression, dExpression};
-  m_expression = new Addition(operands, 4, false);
-  Expression::Simplify(&m_expression, *context);
-  return m_expression;
+  Expression * result = new Addition(operands, 4, false);
+  Expression::Simplify(&result, *context);
+  return result;
 }
 
 double CubicModel::evaluate(double * modelCoefficients, double x) const {
diff --git a/apps/regression/model/cubic_model.h b/apps/regression/model/cubic_model.h
index 2c3359352..ff7405f3b 100644
--- a/apps/regression/model/cubic_model.h
+++ b/apps/regression/model/cubic_model.h
@@ -8,15 +8,13 @@ namespace Regression {
 
 class CubicModel : public Model {
 public:
-  CubicModel() : m_expression(nullptr) {}
+  using Model::Model;
   Poincare::ExpressionLayout * layout() override;
   Poincare::Expression * simplifiedExpression(double * modelCoefficients, Poincare::Context * context) override;
   I18n::Message formulaMessage() const override { return I18n::Message::CubicRegressionFormula; }
   double evaluate(double * modelCoefficients, double x) const override;
   double partialDerivate(double * modelCoefficients, int derivateCoefficientIndex, double x) const override;
   int numberOfCoefficients() const override { return 4; }
-private:
-  Poincare::Expression * m_expression;
 };
 
 }
diff --git a/apps/regression/model/quadratic_model.cpp b/apps/regression/model/quadratic_model.cpp
index 6f4989e2e..33ec1ddfa 100644
--- a/apps/regression/model/quadratic_model.cpp
+++ b/apps/regression/model/quadratic_model.cpp
@@ -31,10 +31,6 @@ ExpressionLayout * QuadraticModel::layout() {
 }
 
 Expression * QuadraticModel::simplifiedExpression(double * modelCoefficients, Poincare::Context * context) {
-  if (m_expression != nullptr) {
-    delete m_expression;
-    m_expression = nullptr;
-  }
   double a = modelCoefficients[0];
   double b = modelCoefficients[1];
   double c = modelCoefficients[2];
@@ -51,9 +47,9 @@ Expression * QuadraticModel::simplifiedExpression(double * modelCoefficients, Po
     false);
   Expression * cExpression = new Decimal(c);
   Expression * const operands[] = {ax2Expression, bxExpression, cExpression};
-  m_expression = new Addition(operands, 3, false);
-  Expression::Simplify(&m_expression, *context);
-  return m_expression;
+  Expression * result = new Addition(operands, 3, false);
+  Expression::Simplify(&result, *context);
+  return result;
 }
 
 double QuadraticModel::evaluate(double * modelCoefficients, double x) const {
diff --git a/apps/regression/model/quadratic_model.h b/apps/regression/model/quadratic_model.h
index a6e8ba9b1..c8481a87a 100644
--- a/apps/regression/model/quadratic_model.h
+++ b/apps/regression/model/quadratic_model.h
@@ -8,15 +8,14 @@ namespace Regression {
 
 class QuadraticModel : public Model {
 public:
-  QuadraticModel() : m_expression(nullptr) {}
+  using Model::Model;
   Poincare::ExpressionLayout * layout() override;
   Poincare::Expression * simplifiedExpression(double * modelCoefficients, Poincare::Context * context) override;
   I18n::Message formulaMessage() const override { return I18n::Message::QuadraticRegressionFormula; }
   double evaluate(double * modelCoefficients, double x) const override;
   double partialDerivate(double * modelCoefficients, int derivateCoefficientIndex, double x) const override;
   int numberOfCoefficients() const override { return 3; }
-private:
-  Poincare::Expression * m_expression;};
+};
 
 }
 
diff --git a/apps/regression/model/quartic_model.cpp b/apps/regression/model/quartic_model.cpp
index 8d9a81b31..883a29f4e 100644
--- a/apps/regression/model/quartic_model.cpp
+++ b/apps/regression/model/quartic_model.cpp
@@ -47,10 +47,6 @@ ExpressionLayout * QuarticModel::layout() {
 }
 
 Expression * QuarticModel::simplifiedExpression(double * modelCoefficients, Poincare::Context * context) {
-  if (m_expression != nullptr) {
-    delete m_expression;
-    m_expression = nullptr;
-  }
   double a = modelCoefficients[0];
   double b = modelCoefficients[1];
   double c = modelCoefficients[2];
@@ -83,9 +79,9 @@ Expression * QuarticModel::simplifiedExpression(double * modelCoefficients, Poin
     false);
   Expression * eExpression = new Decimal(e);
   Expression * const operands[] = {ax4Expression, bx3Expression, cx2Expression, dxExpression, eExpression};
-  m_expression = new Addition(operands, 5, false);
-  Expression::Simplify(&m_expression, *context);
-  return m_expression;
+  Expression * result = new Addition(operands, 5, false);
+  Expression::Simplify(&result, *context);
+  return result;
 }
 
 double QuarticModel::evaluate(double * modelCoefficients, double x) const {
diff --git a/apps/regression/model/quartic_model.h b/apps/regression/model/quartic_model.h
index 897bbc4ed..6c1d2ac46 100644
--- a/apps/regression/model/quartic_model.h
+++ b/apps/regression/model/quartic_model.h
@@ -8,15 +8,13 @@ namespace Regression {
 
 class QuarticModel : public Model {
 public:
-  QuarticModel() : m_expression(nullptr) {}
+  using Model::Model;
   Poincare::ExpressionLayout * layout() override;
   Poincare::Expression * simplifiedExpression(double * modelCoefficients, Poincare::Context * context) override;
   I18n::Message formulaMessage() const override { return I18n::Message::QuarticRegressionFormula; }
   double evaluate(double * modelCoefficients, double x) const override;
   double partialDerivate(double * modelCoefficients, int derivateCoefficientIndex, double x) const override;
   int numberOfCoefficients() const override { return 5; }
-private:
-  Poincare::Expression * m_expression;
 };
 
 }
diff --git a/apps/regression/model/trigonometric_model.cpp b/apps/regression/model/trigonometric_model.cpp
index 8bdd97ea3..8bcaf543e 100644
--- a/apps/regression/model/trigonometric_model.cpp
+++ b/apps/regression/model/trigonometric_model.cpp
@@ -33,10 +33,6 @@ ExpressionLayout * TrigonometricModel::layout() {
 }
 
 Expression * TrigonometricModel::simplifiedExpression(double * modelCoefficients, Poincare::Context * context) {
-  if (m_expression != nullptr) {
-    delete m_expression;
-    m_expression = nullptr;
-  }
   double a = modelCoefficients[0];
   double b = modelCoefficients[1];
   double c = modelCoefficients[2];
@@ -53,9 +49,9 @@ Expression * TrigonometricModel::simplifiedExpression(double * modelCoefficients
       false);
   Expression * asinExpression = new Multiplication(aExpression, sinExpression, false);
   Expression * dExpression = new Decimal(d);
-  m_expression = new Addition(asinExpression, dExpression, false);
-  Expression::Simplify(&m_expression, *context);
-  return m_expression;
+  Expression * result = new Addition(asinExpression, dExpression, false);
+  Expression::Simplify(&result, *context);
+  return result;
 }
 
 double TrigonometricModel::evaluate(double * modelCoefficients, double x) const {
diff --git a/apps/regression/model/trigonometric_model.h b/apps/regression/model/trigonometric_model.h
index ed64d5b9f..8d8602f67 100644
--- a/apps/regression/model/trigonometric_model.h
+++ b/apps/regression/model/trigonometric_model.h
@@ -8,15 +8,13 @@ namespace Regression {
 
 class TrigonometricModel : public Model {
 public:
-  TrigonometricModel() : m_expression(nullptr) {}
+  using Model::Model;
   Poincare::ExpressionLayout * layout() override;
   Poincare::Expression * simplifiedExpression(double * modelCoefficients, Poincare::Context * context) override;
   I18n::Message formulaMessage() const override { return I18n::Message::TrigonometricRegressionFormula; }
   double evaluate(double * modelCoefficients, double x) const override;
   double partialDerivate(double * modelCoefficients, int derivateCoefficientIndex, double x) const override;
   int numberOfCoefficients() const override { return 4; }
-private:
-  Poincare::Expression * m_expression;
 };
 
 }