=3a？ +2b？ -7ab

=3|a|？ +2|b|？ -7 | a | | b | cos & lt； a，b & gt

=3*3? +2*4? -7*3*4cos(3π/4)

=27+32+42√2

=59+42√2

(a+b)？

=a？ +b？ +2ab

=|a|？ +|b|？ +2 | a | | b | cos & lt； a，b & gt

=3? +4? +2*3*4cos(3π/4)

=9+ 16- 12√2

=25- 12√2

2、a+2b

=( 1,-2)+2(-3,4)

=( 1,-2)+(-6,8)

=(-5,6)

(a+2b)*c

=(-5,6)*(3,2)

=-5*3+6*2

=- 15+ 12

=-3

Middle school students' math and physics team wdxf4444 answers for you! I wish you progress in your studies.

You can ask if you don't understand!

If you are satisfied, please click the button below to choose the satisfactory answer, O(∩_∩)O Thank you.