Question

7x3+7y−8y−9x3+8y+7x3
If x=2, y=−1​, the value is:

Answer 1

Answer:

8x-7y=11

7x-8y=4

56x-49y=77

56x-64y=32

___________

15y=45

y=45÷15

y=3

8x-7y=11

8x-7×3=11

8x-21 = 11

8x=11+21

8x=32

x=32÷8

x=4

: X + Y

: 4 + 3

= 7

Answer 2

Adding the given expressions, we have

(i) x3 -2x2y + 3xy2- y3, 2x3- 5xy2 + 3x2y - 4y3

Collecting positive and negative like terms together, we get

x3 +2x3 - 2x2y + 3x2y + 3xy2 - 5xy2 - y3- 4y3

= 3x3 + x2y - 2xy2 - 5y3

(ii) a4 - 2a3b + 3ab3 + 4a2b2 + 3b4, - 2a4 - 5ab3 + 7a3b - 6a2b2 + b4

a4 - 2a3b + 3ab3 + 4a2b2 + 3b4 - 2a4 - 5ab3 + 7a3b - 6a2b2 + b4

Collecting positive and negative like terms together, we get

a4 - 2a4- 2a3b + 7a3b + 3ab3 - 5ab3 + 4a2b2 - 6a2b2 + 3b4 + b4

= - a4 + 5a3b - 2ab3 - 2a2b2 + 4b4.

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