1/7ab+2/3ab=ab*(1/7+2/3)=ab*(3/21+14/21)=ab*17/21
Y=4-x² y=2-x S-?
4-x²=2-x
x²-x-2=0 D=9 √D=3
x₁=-1 x₂=2
S=₋₁²(4-x²-2+x)dx=₋₁²(2+x-x²)dx=(2x+x²/2-x³/3) ₋₁|²=
=2*2+2²/2+2³/3-(2*(-1)+(-1)²/2-(-1)³/3)=4+2-8/3-(-2+1/2+1/3)=6-8/3-(-1,5+1/3)=
=6-8/3+1,5-1/3=7,5-3=4,5.
Ответ: S=4,5 кв. ед.
→ → → → →→<span>
a * b =|a|*|b|*cos</span>∠<span>(ab)
</span>→ →<span>
a* b =2,5*7*cos30=17,5*</span>√3/2=35√3/4