Question

use substitution and elimination method to solve this questions
1. 7x-3y=31
9x-5y=41
2. x-2y-7=0
2x-5y+13=0

3. 2x+y+3=0
4x+2y-1=0

4. x+10y=68
x-y=98

5. x+y=40
x+3y=180​

Answer 1

Answer:

(1)7x-3y=31

take equation (i)

take equation (i)7x-3y=31

take equation (i)7x-3y=317x=31+3y

take equation (i)7x-3y=317x=31+3yx=31+3y/7

take equation (i)7x-3y=317x=31+3yx=31+3y/7now, put the value of x in (2) equation

take equation (i)7x-3y=317x=31+3yx=31+3y/7now, put the value of x in (2) equation9x-5y=41

take equation (i)7x-3y=317x=31+3yx=31+3y/7now, put the value of x in (2) equation9x-5y=419(31+3y/7) -5y=41

take equation (i)7x-3y=317x=31+3yx=31+3y/7now, put the value of x in (2) equation9x-5y=419(31+3y/7) -5y=41279+27y/7-5y=41

take equation (i)7x-3y=317x=31+3yx=31+3y/7now, put the value of x in (2) equation9x-5y=419(31+3y/7) -5y=41279+27y/7-5y=41279+27y-35y/7=41

take equation (i)7x-3y=317x=31+3yx=31+3y/7now, put the value of x in (2) equation9x-5y=419(31+3y/7) -5y=41279+27y/7-5y=41279+27y-35y/7=41279-8y/7=41

take equation (i)7x-3y=317x=31+3yx=31+3y/7now, put the value of x in (2) equation9x-5y=419(31+3y/7) -5y=41279+27y/7-5y=41279+27y-35y/7=41279-8y/7=41279-8y=41×7

take equation (i)7x-3y=317x=31+3yx=31+3y/7now, put the value of x in (2) equation9x-5y=419(31+3y/7) -5y=41279+27y/7-5y=41279+27y-35y/7=41279-8y/7=41279-8y=41×7279-8y=287

take equation (i)7x-3y=317x=31+3yx=31+3y/7now, put the value of x in (2) equation9x-5y=419(31+3y/7) -5y=41279+27y/7-5y=41279+27y-35y/7=41279-8y/7=41279-8y=41×7279-8y=287-8y=287-279

take equation (i)7x-3y=317x=31+3yx=31+3y/7now, put the value of x in (2) equation9x-5y=419(31+3y/7) -5y=41279+27y/7-5y=41279+27y-35y/7=41279-8y/7=41279-8y=41×7279-8y=287-8y=287-279-8y=8

take equation (i)7x-3y=317x=31+3yx=31+3y/7now, put the value of x in (2) equation9x-5y=419(31+3y/7) -5y=41279+27y/7-5y=41279+27y-35y/7=41279-8y/7=41279-8y=41×7279-8y=287-8y=287-279-8y=8y=-8/8

take equation (i)7x-3y=317x=31+3yx=31+3y/7now, put the value of x in (2) equation9x-5y=419(31+3y/7) -5y=41279+27y/7-5y=41279+27y-35y/7=41279-8y/7=41279-8y=41×7279-8y=287-8y=287-279-8y=8y=-8/8y=-1

now put the value of y in first equation