Question

упростите выражение 8/15(2 1/4a-7 1/2b ) -7/30(4 2/7a-8 4/7b)

Answer 1

$\frac8{15}\cdot\left(2\frac14a-7\frac12b\right)-\frac7{30}\cdot\left(4\frac27a-8\frac74b\right)=\bold{\frac15a-2b}\\\\1)\;\frac8{15}\cdot\left(2\frac14a-7\frac12b\right)=\frac8{15}\cdot\left(\frac94a-\frac{15}2b\right)=\frac8{15}\cdot\frac94a-\frac8{15}\cdot\frac{15}2b=\\\\=\frac25\cdot\frac31a-4b=\frac65a-4b=1\frac15a-4b$

$2)\;\frac7{30}\cdot\left(4\frac27a-8\frac47b\right)=\frac7{30}\cdot\left(\frac{30}7a-\frac{60}7b\right)=\frac7{30}\cdot\frac{30}7a-\frac7{30}\cdot\frac{60}7b=\\\\=a-2b$

$3)\;\left(1\frac15a-4b\right)-\left(a-2b\right)=1\frac15a-4b-a+2b=\frac15a-2b$