Question

1.Tính nhanh

b. 4.(-5)² + 2.(-5) - 20

c. 27.(15-12) - 15.(27-12)

Answer 1

\(b)4\cdot(-5)^2+2\cdot(-5)-20\)

\(=4\cdot25+2\cdot(-5)-20\)

\(=100+(-10)-20=70\)

\(c)27\cdot(15-12)-15\cdot(27-12)\)

\(=27\cdot15-27\cdot12-15\cdot27-15\cdot12\)

\(=(27\cdot15-15\cdot27)-27\cdot12-15\cdot12\)

\(=0-(27-15)\cdot12=0-12\cdot12=0-144=-144\)

Answer 2

a)

4.25+2.(-5)-20

=100+-10-20

=90-20

=70

c)

=27.15 - 27.12- 15.27 + 15.12

=(27.15-15.27)-27.12+15.12

=0-12.(27+15)

=0-12.42

=0-504

=-504

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Hok tốt

Answer 3

\(b,4\cdot\left(-5\right)^2+2\cdot\left(-5\right)-20\)

\(=\left(-5\right)\cdot\left[4\cdot\left(-5\right)+2+\left(-4\right)\right]\)

\(=\left(-5\right)\cdot\left(-22\right)=110\)