Question

1)
1)
(5x - 2)(a + 3)
27 (a- 1)(b + 1)
37 (2c² – 1) (d + 2)
Q:4 Expand:
(5 - 8mn)
2) (2a -}
2:5 Prove:
1)
(2x + 5)2 – (2x - 5)2 = 40x
27 (2ab + 3c)? - (2ab - 3c)? - 24 abc = 0
2:6 Evaluate:
1)
2) 61 X 56
27 × 32​

Answer 1

Answer:

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Answer 2

Answer:

1) (2x+5)²-(2x-5)²=40x.

(2x+5)².

By using formula (a+b)²=a²+2ab+b² where a=2x & b=5.

(2x+5)²=(2x)²+2(2x)(5)+(5)².

=4x²+20x+25.

(2x-5)².

By using formula (a-b)²=a²-2ab+b² where a=2x & b=5.

(2x-5)²=(2x)²-2(2x)(5)+(5)².

=4x²-20x+25.

(2x+5)²-(2x-5)²=(4x²+20x+25)-(4x²-20x+25).

=4x²+20x+25-4x²+20x-25. (Because -×-=+ & -×+=-).

=20x+20x. (Because +×-=- so, 4x²-4x² & 25-25 will cancel i.e., it will be zero(0)).

=40x.

2) (2ab+3c)?-(2ab-3c)?-24abc=0.

(2ab+3c)².

By using formula (a+b)²=a²+2ab+b² where a=2ab & b=3c.

(2ab+3c)²=(2ab)²+2(2ab)(3c)+(3c)².

=4a²b²+12abc+9c².

(2ab-3c)².

By using formula (a-b)²=a²-2ab+b² where a=2ab & b=3c.

(2ab-3c)²=(2ab)²-2(2ab)(3c)+(3c)².

=4a²b²-12abc+9c².

(2ab+3c)²-(2ab-3c)²-24abc=(4a²b²+12abc+9c²)-(4a²b²-12abc+9c²)-24abc.

=4a²b²+12abc+9c²-4a²b²+12abc-9c²-24abc. (Because -×-=+ & -×+=-).

=12abc+12abc-24abc. (Because +×-=- so, 4a²b²-4a²b² & 9c²-9c² will cancel i.e., it will be zero(0)).

=24abc-24abc.

=0. (Because +×-=- so, 24abc-24abc will cancel i.e., it will be zero(0)).

So, (2ab+3c)²-(2ab-3c)²-24abc=0 is your answer.

Sorry i didn't understand other questions.

I think this is your answer.