Bài 2 tính nhanh a, 26×7-17×9+13×26-17×11 B,32×19+32

Đáp án:

$\text{a) 180.}$

$\text{b) 640.}$

Giải thích các bước giải:

$\text{a) 26 × 7 – 17 × 9 + 13 × 26 – 17 × 11.}$

$\text{= (26 × 7 + 13 × 26) – (17 × 9 + 17 × 11).}$

$\text{= 26 × (7 + 13) – 17 × (9 + 11).}$

$\text{= 26 × 20 – 17 × 20.}$

$\text{= (26 – 17) × 20.}$

$\text{= 9 × 20.}$

$\text{= 180.}$

$\text{b) 32 × 19 + 32.}$

$\text{= 32 × 19 + 32 × 1.}$

$\text{= 32 × (19 + 1).}$

$\text{= 32 × 20.}$

$\text{= 640.}$