Tính (x^2 + 2x + 3) + (3x^2 – 5x + 1)

---

Tính:

Giải vở bài tập Toán 7 Bài tập cuối chương 6

Câu 7 trang 63 vở bài tập Toán lớp 7 Tập 2: Tính:

a) (x² + 2x + 3) + (3x² – 5x + 1)

.........................................................................................................................

.........................................................................................................................

.........................................................................................................................

b) ( 4x³ – 2x² – 6 ) – ( x³ – 7x² + x – 5 )

.........................................................................................................................

.........................................................................................................................

.........................................................................................................................

c) ( –3x² )( 6x² – 8x + 1)

.........................................................................................................................

.........................................................................................................................

.........................................................................................................................

d) ( 4x² + 2x + 1)( 2x – 1 )

.........................................................................................................................

.........................................................................................................................

.........................................................................................................................

e) (x⁶ – 2x⁴ + x² ) : ( –2x² )

.........................................................................................................................

.........................................................................................................................

.........................................................................................................................

g) ( x⁵ – x⁴ – 2x³ ) : ( x² + x)

.........................................................................................................................

.........................................................................................................................

.........................................................................................................................

Lời giải:

a) ( x² + 2x + 3) + (3x² – 5x + 1)

= x² + 3x² + 2x – 5x + 3 + 1

= 4x² – 3x + 4.

b) (4x³ – 2x² – 6) – (x³ – 7x² + x – 5)

= 4x³ – 2x² – 6 – x³ + 7x² – x + 5

= 4x³ – x³ – 2x² + 7x² – x – 6 + 5

= 3x³ + 5x² – x – 1.

c) (–3x²)(6x² – 8x + 1)

= (–3x²).6x² + (–3x²).(–8x) + (–3x²).1

= –18x⁴ + 24x³ – 3x² d) (4x² + 2x + 1)(2x – 1)

= 4x².2x + 2x.2x + 2x – 4x² – 2x – 1

= 8x³ + 4x² + 2x – 4x² – 2x – 1 = 8x³ – 1

e) (x⁶ – 2x⁴ + x²) : (–2x²)

= x⁶ : (–2x²) – 2x⁴ : (–2x²) + x² : (–2x²)

= $\frac{-1}{2}$. x^{6 – 2} + x^{4 – 2} – $\frac{1}{2}$

= $\frac{-1}{2}$x⁴ + x² – $\frac{1}{2}$.

g) (x⁵ – x⁴ – 2x³) : (x² + x)

Vậy ( x⁵ – x⁴ – 2x³ ) : ( x² + x) = x³ – 2x² .