Question

how to substitute the value 3x+7y
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Answer 1

ᴀɴsᴡᴇʀ

ɢɪᴠᴇɴ ᴇϙᴜᴀᴛɪᴏɴs ᴀʀᴇ,

3x+7ʏ=32 .....(1)

ᴀɴᴅ 7x+3ʏ=48 .....(2)

sᴛᴇᴘ 1: ᴀᴅᴅɪɴɢ ʙᴏᴛʜ ᴛʜᴇ ᴇϙᴜᴀᴛɪᴏɴs, ᴡᴇ ɢᴇᴛ

10x+10ʏ=80

⇒10(x+ʏ)=10×8

⇒x+ʏ=8 .....(3)

sᴛᴇᴘ 2: sᴜʙᴛʀᴀᴄᴛɪɴɢ ᴇϙᴜᴀᴛɪᴏɴ (1) ғʀᴏᴍ ᴇϙᴜᴀᴛɪᴏɴ (2),

(7x+3ʏ)−(3x+7ʏ)=48−32

⇒4x−4ʏ=16

⇒4(x−ʏ)=4×4

⇒x−ʏ=4 .......(4)

sᴛᴇᴘ 3: ᴀᴅᴅɪɴɢ ᴇϙᴜᴀᴛɪᴏɴs (3) ᴀɴᴅ (4), ᴡᴇ ɢᴇᴛ

x+ʏ+x−ʏ=12

⇒2x=12

⇒x=6

sᴜʙsᴛɪᴛᴜᴛɪɴɢ x=6 ɪɴ ᴀɴʏ ᴏғ ᴛʜᴇ ᴇϙᴜᴀᴛɪᴏɴs (1), ᴡᴇ ɢᴇᴛ ʏ=2

∴ ᴛʜᴇ sᴏʟᴜᴛɪᴏɴs ᴏғ ᴛʜᴇ ᴘᴀɪʀ ᴏғ ᴇϙᴜᴀᴛɪᴏɴs ɪs x=6 ᴀɴᴅ ʏ=2.