Question

4a^2+9b^2-(2a-3b)^2 при а=-15,1 b=1/2

Answer 1

4a²+9b²-(2a-3b)²=4a²+9b²-(4a²-12ab+9b²)=
=4a²+9b²-4a²+12ab-9b²=12ab

12ab=12.(-15).(1/2)=6.(-15)=-90

Answer 2

To find the value of the expression 4a^2 + 9b^2 - (2a - 3b)^2 when a = -15 and b = 1/2, we can substitute these values into the expression and simplify it.

Let's start by substituting the given values into the expression:

4a^2 + 9b^2 - (2a - 3b)^2

Substituting a = -15 and b = 1/2:

4(-15)^2 + 9(1/2)^2 - (2(-15) - 3(1/2))^2

Simplifying the exponents:

4(225) + 9(1/4) - (2(-15) - 3(1/2))^2

Multiplying:

900 + 9/4 - (2(-15) - 3(1/2))^2

Simplifying the negative sign:

900 + 9/4 - (2(-15) + (-3)(1/2))^2

Multiplying:

900 + 9/4 - (2(-15) + (-3/2))^2

Simplifying the parentheses:

900 + 9/4 - (-30 - 3/2)^2

Adding:

900 + 9/4 - (-60/2 - 3/2)^2

Simplifying the fractions:

900 + 9/4 - (-63/2)^2

Simplifying the exponent:

900 + 9/4 - 3969/4

Combining the fractions:

900 + (9 - 3969)/4

Subtracting:

900 - 3960/4

Simplifying the fraction:

900 - 990

Calculating:

-90

Therefore, when a = -15 and b = 1/2, the value of the expression 4a^2 + 9b^2 - (2a - 3b)^2 is -90.