Question

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Answer 1

Q. 17)

What should be added to 2a²-7ab+5b² to obtain a²+4ab-3b² ?

Solution-

The number to be added

= (a²+4ab-3b²)-(2a²-7ab+5b²)

= a²+4ab-3b²-2a²+7ab-5b²

= (a²-2a²)+(4ab+7ab)+(-3b²-5b²)

= -a²+11ab-8b²

Hence, the number that should be added to 2a²-7ab+5b² to obtain a²+4ab-3b² is -a²+11ab-8b².

Q. 18)

What should be subtracted from 2a+8b+10 to get -4a+3b+12?

Solution-

The number to be subtracted

= (2a+8b+10)-(-4a+3b+12)

= 2a+8b+10+4a-3b-12

= (2a+4a)+(8b-3b)+(10-12)

= 6a+5b-2

Hence, the number that should be subtracted from 2a+8b+10 to get -4a+3b+12 is 6a+5b-2.

Hope this helps you to get to your answer.

Answer 2

Answer:

17) (a² + 4ab - 3b²) - (2a² - 7ab + 5b²)

= a² + 4ab - 3b² - 2a² + 7ab - 5b²

= a² - 2a² + 4ab + 7ab - 3b² - 5b²

= -a² + 11ab - 8b²

18) (2a + 8b + 10) - (-4a + 3b + 12)

= 2a + 8b + 10 + 4a - 3b - 12

= 2a + 4a + 8b - 3b + 10 - 12

= 6a + 5b - 2